diff --git a/assignment5/Question1/BadSpeedSetting.java b/assignment5/Question1/BadSpeedSetting.java
new file mode 100644
index 0000000..2a08413
--- /dev/null
+++ b/assignment5/Question1/BadSpeedSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadSpeedSetting class is used to test the speed of the program.
+ */
+public class BadSpeedSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadSpeedSetting.class.getName().hashCode();
+
+	public BadSpeedSetting() {
+		super();
+	}
+
+	public BadSpeedSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question1/ExceedSpeedLimit.java b/assignment5/Question1/ExceedSpeedLimit.java
new file mode 100644
index 0000000..ce76da8
--- /dev/null
+++ b/assignment5/Question1/ExceedSpeedLimit.java
@@ -0,0 +1,15 @@
+/*
+ * The ExceedSpeedLimit class is used to check if the speed limit is exceeded
+ */
+public class ExceedSpeedLimit extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = ExceedSpeedLimit.class.getName().hashCode();
+
+	public ExceedSpeedLimit() {
+		super();
+	}
+
+	public ExceedSpeedLimit(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question1/Movable.java b/assignment5/Question1/Movable.java
new file mode 100644
index 0000000..8db52d5
--- /dev/null
+++ b/assignment5/Question1/Movable.java
@@ -0,0 +1,9 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is a moveable interface.
+ */
+
+public interface Movable {
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed;
+}
diff --git a/assignment5/Question1/NotEnoughSpeed.java b/assignment5/Question1/NotEnoughSpeed.java
new file mode 100644
index 0000000..b864e1f
--- /dev/null
+++ b/assignment5/Question1/NotEnoughSpeed.java
@@ -0,0 +1,15 @@
+/*
+ * The NotEnoughSpeed class is used to test the speed of the program.
+ */
+public class NotEnoughSpeed extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = NotEnoughSpeed.class.getName().hashCode();
+
+	public NotEnoughSpeed() {
+		super();
+	}
+
+	public NotEnoughSpeed(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question1/Start.java b/assignment5/Question1/Start.java
new file mode 100644
index 0000000..a21b424
--- /dev/null
+++ b/assignment5/Question1/Start.java
@@ -0,0 +1,5 @@
+public class Start {
+	public static void main(String[] args) {
+		Vehicle.testVehicle();
+	}
+}
diff --git a/assignment5/Question1/Vehicle.java b/assignment5/Question1/Vehicle.java
new file mode 100644
index 0000000..0d77748
--- /dev/null
+++ b/assignment5/Question1/Vehicle.java
@@ -0,0 +1,180 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is the abstract Vehicle class.
+ */
+
+public abstract class Vehicle implements Movable {
+	private int speedLimit;
+	private int speed;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the vehicle
+	 * @param speed      the speed of the vehicle
+	 * @throws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *                         is greater than speed limit.
+	 */
+	public Vehicle(int speedLimit, int speed) throws BadSpeedSetting {
+		if (speedLimit < 0 || speed < 0) {
+			throw new BadSpeedSetting("Speed cannot be negative!");
+		}
+		if (speed > speedLimit) {
+			throw new BadSpeedSetting("Speed cannot be greater than speed limit!");
+		}
+		this.speedLimit = speedLimit;
+		this.speed = speed;
+	}
+
+	/**
+	 * Getter of speed.
+	 *
+	 * @return the speed of the vehicle
+	 */
+	public int getSpeed() {
+		return speed;
+	}
+
+	/**
+	 * Accelerate the vehicle.
+	 *
+	 * @param amount the amount of acceleration.
+	 * @throws ExceedSpeedLimit if the speed is greater than speed limit after
+	 *                          increased.
+	 * @thorws NotEnoughSpeed if the speed is less than 0 after decreased.
+	 * @return the new speed of the vehicle
+	 */
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed {
+		int newSpeed = speed + amount;
+		if (newSpeed > speedLimit) {
+			throw new ExceedSpeedLimit(
+					String.format("Current speed is %d. Accelerate %d will exceed the speed limit!",
+							speed, amount));
+		}
+		if (newSpeed < 0) {
+			throw new NotEnoughSpeed(
+					String.format("Current speed is %d, not enough speed to decelerate!", speed));
+		}
+		speed = newSpeed;
+		return speed;
+	}
+
+	/**
+	 * Whether the vehicle can fly or not.
+	 *
+	 * @return whether the vehicle can fly.
+	 */
+	public abstract boolean canFly();
+
+	/**
+	 * Test.
+	 */
+	public static void testVehicle() {
+		try {
+			Vehicle car;
+			try {
+				car = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				car = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			car = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return false;
+				}
+			};
+			System.out.println(car.getSpeed() == 50);
+			System.out.println(car.canFly() == false);
+			System.out.println(car.accelerate(10) == 60);
+			System.out.println(car.accelerate(10) == 70);
+			System.out.println(car.accelerate(10) == 80);
+			System.out.println(car.accelerate(10) == 90);
+			System.out.println(car.accelerate(10) == 100);
+			try {
+				System.out.println(car.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(car.accelerate(-50) == 50);
+			System.out.println(car.accelerate(-50) == 0);
+			try {
+				System.out.println(car.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Vehicle plane;
+			try {
+				plane = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				plane = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			plane = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return true;
+				}
+			};
+			System.out.println(plane.getSpeed() == 50);
+			System.out.println(plane.canFly() == true);
+			System.out.println(plane.accelerate(10) == 60);
+			System.out.println(plane.accelerate(10) == 70);
+			System.out.println(plane.accelerate(10) == 80);
+			System.out.println(plane.accelerate(10) == 90);
+			System.out.println(plane.accelerate(10) == 100);
+			try {
+				System.out.println(plane.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(plane.accelerate(-50) == 50);
+			System.out.println(plane.accelerate(-50) == 0);
+			try {
+				System.out.println(plane.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: Uncatched exception!");
+		}
+	}
+}
diff --git a/assignment5/Question2/BadSpeedSetting.java b/assignment5/Question2/BadSpeedSetting.java
new file mode 100644
index 0000000..2a08413
--- /dev/null
+++ b/assignment5/Question2/BadSpeedSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadSpeedSetting class is used to test the speed of the program.
+ */
+public class BadSpeedSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadSpeedSetting.class.getName().hashCode();
+
+	public BadSpeedSetting() {
+		super();
+	}
+
+	public BadSpeedSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question2/Car.java b/assignment5/Question2/Car.java
new file mode 100644
index 0000000..7017ab2
--- /dev/null
+++ b/assignment5/Question2/Car.java
@@ -0,0 +1,130 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Car class
+ */
+
+public class Car extends Vehicle {
+
+	/**
+	 * Car can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit The speed limit of the car.
+	 * @param speed      the speed of the car.
+	 * @thorws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *         is greater than the speed limit.
+	 */
+	public Car(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Constructor. Default speed limit is 120.
+	 *
+	 * @param speed the speed of the car.
+	 * @thorws BadSpeedSetting if speed is negative. Or if the speed is greater than
+	 *         the speed limit 120.
+	 */
+	public Car(int speed) throws BadSpeedSetting {
+		this(120, speed);
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testCar() {
+		try {
+			Car c1;
+			try {
+				c1 = new Car(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, 121);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			c1 = new Car(120, 100);
+			System.out.println(c1.getSpeed() == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 110);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 120);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c1.accelerate(-20) == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 80);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 60);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 40);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 20);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 0);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Car c2 = new Car(100);
+			System.out.println(c2.getSpeed() == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 110);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 120);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c2.accelerate(-20) == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 80);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 60);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 40);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 20);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 0);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error uncatched exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question2/ExceedSpeedLimit.java b/assignment5/Question2/ExceedSpeedLimit.java
new file mode 100644
index 0000000..ce76da8
--- /dev/null
+++ b/assignment5/Question2/ExceedSpeedLimit.java
@@ -0,0 +1,15 @@
+/*
+ * The ExceedSpeedLimit class is used to check if the speed limit is exceeded
+ */
+public class ExceedSpeedLimit extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = ExceedSpeedLimit.class.getName().hashCode();
+
+	public ExceedSpeedLimit() {
+		super();
+	}
+
+	public ExceedSpeedLimit(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question2/Movable.java b/assignment5/Question2/Movable.java
new file mode 100644
index 0000000..8db52d5
--- /dev/null
+++ b/assignment5/Question2/Movable.java
@@ -0,0 +1,9 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is a moveable interface.
+ */
+
+public interface Movable {
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed;
+}
diff --git a/assignment5/Question2/NotEnoughSpeed.java b/assignment5/Question2/NotEnoughSpeed.java
new file mode 100644
index 0000000..b864e1f
--- /dev/null
+++ b/assignment5/Question2/NotEnoughSpeed.java
@@ -0,0 +1,15 @@
+/*
+ * The NotEnoughSpeed class is used to test the speed of the program.
+ */
+public class NotEnoughSpeed extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = NotEnoughSpeed.class.getName().hashCode();
+
+	public NotEnoughSpeed() {
+		super();
+	}
+
+	public NotEnoughSpeed(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question2/Start.java b/assignment5/Question2/Start.java
new file mode 100644
index 0000000..bb07732
--- /dev/null
+++ b/assignment5/Question2/Start.java
@@ -0,0 +1,6 @@
+public class Start {
+	public static void main(String[] args) {
+		Vehicle.testVehicle();
+		Car.testCar();
+	}
+}
diff --git a/assignment5/Question2/Vehicle.java b/assignment5/Question2/Vehicle.java
new file mode 100644
index 0000000..0d77748
--- /dev/null
+++ b/assignment5/Question2/Vehicle.java
@@ -0,0 +1,180 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is the abstract Vehicle class.
+ */
+
+public abstract class Vehicle implements Movable {
+	private int speedLimit;
+	private int speed;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the vehicle
+	 * @param speed      the speed of the vehicle
+	 * @throws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *                         is greater than speed limit.
+	 */
+	public Vehicle(int speedLimit, int speed) throws BadSpeedSetting {
+		if (speedLimit < 0 || speed < 0) {
+			throw new BadSpeedSetting("Speed cannot be negative!");
+		}
+		if (speed > speedLimit) {
+			throw new BadSpeedSetting("Speed cannot be greater than speed limit!");
+		}
+		this.speedLimit = speedLimit;
+		this.speed = speed;
+	}
+
+	/**
+	 * Getter of speed.
+	 *
+	 * @return the speed of the vehicle
+	 */
+	public int getSpeed() {
+		return speed;
+	}
+
+	/**
+	 * Accelerate the vehicle.
+	 *
+	 * @param amount the amount of acceleration.
+	 * @throws ExceedSpeedLimit if the speed is greater than speed limit after
+	 *                          increased.
+	 * @thorws NotEnoughSpeed if the speed is less than 0 after decreased.
+	 * @return the new speed of the vehicle
+	 */
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed {
+		int newSpeed = speed + amount;
+		if (newSpeed > speedLimit) {
+			throw new ExceedSpeedLimit(
+					String.format("Current speed is %d. Accelerate %d will exceed the speed limit!",
+							speed, amount));
+		}
+		if (newSpeed < 0) {
+			throw new NotEnoughSpeed(
+					String.format("Current speed is %d, not enough speed to decelerate!", speed));
+		}
+		speed = newSpeed;
+		return speed;
+	}
+
+	/**
+	 * Whether the vehicle can fly or not.
+	 *
+	 * @return whether the vehicle can fly.
+	 */
+	public abstract boolean canFly();
+
+	/**
+	 * Test.
+	 */
+	public static void testVehicle() {
+		try {
+			Vehicle car;
+			try {
+				car = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				car = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			car = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return false;
+				}
+			};
+			System.out.println(car.getSpeed() == 50);
+			System.out.println(car.canFly() == false);
+			System.out.println(car.accelerate(10) == 60);
+			System.out.println(car.accelerate(10) == 70);
+			System.out.println(car.accelerate(10) == 80);
+			System.out.println(car.accelerate(10) == 90);
+			System.out.println(car.accelerate(10) == 100);
+			try {
+				System.out.println(car.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(car.accelerate(-50) == 50);
+			System.out.println(car.accelerate(-50) == 0);
+			try {
+				System.out.println(car.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Vehicle plane;
+			try {
+				plane = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				plane = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			plane = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return true;
+				}
+			};
+			System.out.println(plane.getSpeed() == 50);
+			System.out.println(plane.canFly() == true);
+			System.out.println(plane.accelerate(10) == 60);
+			System.out.println(plane.accelerate(10) == 70);
+			System.out.println(plane.accelerate(10) == 80);
+			System.out.println(plane.accelerate(10) == 90);
+			System.out.println(plane.accelerate(10) == 100);
+			try {
+				System.out.println(plane.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(plane.accelerate(-50) == 50);
+			System.out.println(plane.accelerate(-50) == 0);
+			try {
+				System.out.println(plane.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: Uncatched exception!");
+		}
+	}
+}
diff --git a/assignment5/Question3/Aircraft.java b/assignment5/Question3/Aircraft.java
new file mode 100644
index 0000000..c234253
--- /dev/null
+++ b/assignment5/Question3/Aircraft.java
@@ -0,0 +1,127 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Aircraft.java inherited from Vehicle class
+ */
+
+public class Aircraft extends Vehicle {
+	/**
+	 * The altitude at which the aircraft is flying.
+	 */
+	private int altitude;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the aircraft
+	 * @param speed      the speed of the aircraft
+	 * @param altitude   the altitude of the aircraft
+	 * @throws BadSpeedSetting    if the speed limit is negative
+	 * @throws BadAltitudeSetting if the altitude is negative
+	 */
+	public Aircraft(int speedLimit, int speed, int altitude) throws BadSpeedSetting, BadAltitudeSetting {
+		super(speedLimit, speed);
+		if (altitude < 0) {
+			throw new BadAltitudeSetting("Altitude cannot be negative!");
+		}
+		this.altitude = altitude;
+	}
+
+	/**
+	 * Getter of altitude.
+	 *
+	 * @return the altitude of the aircraft
+	 */
+	public int getAltitude() {
+		return altitude;
+	}
+
+	/**
+	 * Aircraft can fly.
+	 *
+	 * @return true
+	 */
+	@Override
+	public boolean canFly() {
+		return true;
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testAircraft() {
+		try {
+			Aircraft aircraft;
+
+			try {
+				aircraft = new Aircraft(-10, 10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, -10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, 10, -10);
+			} catch (BadAltitudeSetting e) {
+				System.out.println(e.getMessage().equals("Altitude cannot be negative!"));
+			}
+
+			aircraft = new Aircraft(100, 50, 3900);
+			System.out.println(aircraft.getAltitude() == 3900);
+			System.out.println(aircraft.getSpeed() == 50);
+			System.out.println(aircraft.canFly() == true);
+			// acceleration
+			System.out.println(aircraft.accelerate(10) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 70);
+			System.out.println(aircraft.getSpeed() == 70);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 90);
+			System.out.println(aircraft.getSpeed() == 90);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 100);
+			System.out.println(aircraft.getSpeed() == 100);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			// deceleration
+			System.out.println(aircraft.accelerate(-20) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 40);
+			System.out.println(aircraft.getSpeed() == 40);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 20);
+			System.out.println(aircraft.getSpeed() == 20);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 0);
+			System.out.println(aircraft.getSpeed() == 0);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+		} catch (Exception e) {
+			System.out.println("Error uncaught exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question3/BadAltitudeSetting.java b/assignment5/Question3/BadAltitudeSetting.java
new file mode 100644
index 0000000..c2a1506
--- /dev/null
+++ b/assignment5/Question3/BadAltitudeSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadAltitudeSetting class is used to test the speed of the program.
+ */
+public class BadAltitudeSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadAltitudeSetting.class.getName().hashCode();
+
+	public BadAltitudeSetting() {
+		super();
+	}
+
+	public BadAltitudeSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question3/BadSpeedSetting.java b/assignment5/Question3/BadSpeedSetting.java
new file mode 100644
index 0000000..2a08413
--- /dev/null
+++ b/assignment5/Question3/BadSpeedSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadSpeedSetting class is used to test the speed of the program.
+ */
+public class BadSpeedSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadSpeedSetting.class.getName().hashCode();
+
+	public BadSpeedSetting() {
+		super();
+	}
+
+	public BadSpeedSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question3/Car.java b/assignment5/Question3/Car.java
new file mode 100644
index 0000000..7017ab2
--- /dev/null
+++ b/assignment5/Question3/Car.java
@@ -0,0 +1,130 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Car class
+ */
+
+public class Car extends Vehicle {
+
+	/**
+	 * Car can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit The speed limit of the car.
+	 * @param speed      the speed of the car.
+	 * @thorws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *         is greater than the speed limit.
+	 */
+	public Car(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Constructor. Default speed limit is 120.
+	 *
+	 * @param speed the speed of the car.
+	 * @thorws BadSpeedSetting if speed is negative. Or if the speed is greater than
+	 *         the speed limit 120.
+	 */
+	public Car(int speed) throws BadSpeedSetting {
+		this(120, speed);
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testCar() {
+		try {
+			Car c1;
+			try {
+				c1 = new Car(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, 121);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			c1 = new Car(120, 100);
+			System.out.println(c1.getSpeed() == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 110);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 120);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c1.accelerate(-20) == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 80);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 60);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 40);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 20);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 0);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Car c2 = new Car(100);
+			System.out.println(c2.getSpeed() == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 110);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 120);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c2.accelerate(-20) == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 80);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 60);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 40);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 20);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 0);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error uncatched exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question3/ExceedSpeedLimit.java b/assignment5/Question3/ExceedSpeedLimit.java
new file mode 100644
index 0000000..ce76da8
--- /dev/null
+++ b/assignment5/Question3/ExceedSpeedLimit.java
@@ -0,0 +1,15 @@
+/*
+ * The ExceedSpeedLimit class is used to check if the speed limit is exceeded
+ */
+public class ExceedSpeedLimit extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = ExceedSpeedLimit.class.getName().hashCode();
+
+	public ExceedSpeedLimit() {
+		super();
+	}
+
+	public ExceedSpeedLimit(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question3/Movable.java b/assignment5/Question3/Movable.java
new file mode 100644
index 0000000..8db52d5
--- /dev/null
+++ b/assignment5/Question3/Movable.java
@@ -0,0 +1,9 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is a moveable interface.
+ */
+
+public interface Movable {
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed;
+}
diff --git a/assignment5/Question3/NotEnoughSpeed.java b/assignment5/Question3/NotEnoughSpeed.java
new file mode 100644
index 0000000..b864e1f
--- /dev/null
+++ b/assignment5/Question3/NotEnoughSpeed.java
@@ -0,0 +1,15 @@
+/*
+ * The NotEnoughSpeed class is used to test the speed of the program.
+ */
+public class NotEnoughSpeed extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = NotEnoughSpeed.class.getName().hashCode();
+
+	public NotEnoughSpeed() {
+		super();
+	}
+
+	public NotEnoughSpeed(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question3/Start.java b/assignment5/Question3/Start.java
new file mode 100644
index 0000000..f073de9
--- /dev/null
+++ b/assignment5/Question3/Start.java
@@ -0,0 +1,7 @@
+public class Start {
+	public static void main(String[] args) {
+		Vehicle.testVehicle();
+		Car.testCar();
+		Aircraft.testAircraft();
+	}
+}
diff --git a/assignment5/Question3/Vehicle.java b/assignment5/Question3/Vehicle.java
new file mode 100644
index 0000000..0d77748
--- /dev/null
+++ b/assignment5/Question3/Vehicle.java
@@ -0,0 +1,180 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is the abstract Vehicle class.
+ */
+
+public abstract class Vehicle implements Movable {
+	private int speedLimit;
+	private int speed;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the vehicle
+	 * @param speed      the speed of the vehicle
+	 * @throws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *                         is greater than speed limit.
+	 */
+	public Vehicle(int speedLimit, int speed) throws BadSpeedSetting {
+		if (speedLimit < 0 || speed < 0) {
+			throw new BadSpeedSetting("Speed cannot be negative!");
+		}
+		if (speed > speedLimit) {
+			throw new BadSpeedSetting("Speed cannot be greater than speed limit!");
+		}
+		this.speedLimit = speedLimit;
+		this.speed = speed;
+	}
+
+	/**
+	 * Getter of speed.
+	 *
+	 * @return the speed of the vehicle
+	 */
+	public int getSpeed() {
+		return speed;
+	}
+
+	/**
+	 * Accelerate the vehicle.
+	 *
+	 * @param amount the amount of acceleration.
+	 * @throws ExceedSpeedLimit if the speed is greater than speed limit after
+	 *                          increased.
+	 * @thorws NotEnoughSpeed if the speed is less than 0 after decreased.
+	 * @return the new speed of the vehicle
+	 */
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed {
+		int newSpeed = speed + amount;
+		if (newSpeed > speedLimit) {
+			throw new ExceedSpeedLimit(
+					String.format("Current speed is %d. Accelerate %d will exceed the speed limit!",
+							speed, amount));
+		}
+		if (newSpeed < 0) {
+			throw new NotEnoughSpeed(
+					String.format("Current speed is %d, not enough speed to decelerate!", speed));
+		}
+		speed = newSpeed;
+		return speed;
+	}
+
+	/**
+	 * Whether the vehicle can fly or not.
+	 *
+	 * @return whether the vehicle can fly.
+	 */
+	public abstract boolean canFly();
+
+	/**
+	 * Test.
+	 */
+	public static void testVehicle() {
+		try {
+			Vehicle car;
+			try {
+				car = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				car = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			car = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return false;
+				}
+			};
+			System.out.println(car.getSpeed() == 50);
+			System.out.println(car.canFly() == false);
+			System.out.println(car.accelerate(10) == 60);
+			System.out.println(car.accelerate(10) == 70);
+			System.out.println(car.accelerate(10) == 80);
+			System.out.println(car.accelerate(10) == 90);
+			System.out.println(car.accelerate(10) == 100);
+			try {
+				System.out.println(car.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(car.accelerate(-50) == 50);
+			System.out.println(car.accelerate(-50) == 0);
+			try {
+				System.out.println(car.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Vehicle plane;
+			try {
+				plane = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				plane = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			plane = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return true;
+				}
+			};
+			System.out.println(plane.getSpeed() == 50);
+			System.out.println(plane.canFly() == true);
+			System.out.println(plane.accelerate(10) == 60);
+			System.out.println(plane.accelerate(10) == 70);
+			System.out.println(plane.accelerate(10) == 80);
+			System.out.println(plane.accelerate(10) == 90);
+			System.out.println(plane.accelerate(10) == 100);
+			try {
+				System.out.println(plane.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(plane.accelerate(-50) == 50);
+			System.out.println(plane.accelerate(-50) == 0);
+			try {
+				System.out.println(plane.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: Uncatched exception!");
+		}
+	}
+}
diff --git a/assignment5/Question4/Aircraft.java b/assignment5/Question4/Aircraft.java
new file mode 100644
index 0000000..c234253
--- /dev/null
+++ b/assignment5/Question4/Aircraft.java
@@ -0,0 +1,127 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Aircraft.java inherited from Vehicle class
+ */
+
+public class Aircraft extends Vehicle {
+	/**
+	 * The altitude at which the aircraft is flying.
+	 */
+	private int altitude;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the aircraft
+	 * @param speed      the speed of the aircraft
+	 * @param altitude   the altitude of the aircraft
+	 * @throws BadSpeedSetting    if the speed limit is negative
+	 * @throws BadAltitudeSetting if the altitude is negative
+	 */
+	public Aircraft(int speedLimit, int speed, int altitude) throws BadSpeedSetting, BadAltitudeSetting {
+		super(speedLimit, speed);
+		if (altitude < 0) {
+			throw new BadAltitudeSetting("Altitude cannot be negative!");
+		}
+		this.altitude = altitude;
+	}
+
+	/**
+	 * Getter of altitude.
+	 *
+	 * @return the altitude of the aircraft
+	 */
+	public int getAltitude() {
+		return altitude;
+	}
+
+	/**
+	 * Aircraft can fly.
+	 *
+	 * @return true
+	 */
+	@Override
+	public boolean canFly() {
+		return true;
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testAircraft() {
+		try {
+			Aircraft aircraft;
+
+			try {
+				aircraft = new Aircraft(-10, 10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, -10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, 10, -10);
+			} catch (BadAltitudeSetting e) {
+				System.out.println(e.getMessage().equals("Altitude cannot be negative!"));
+			}
+
+			aircraft = new Aircraft(100, 50, 3900);
+			System.out.println(aircraft.getAltitude() == 3900);
+			System.out.println(aircraft.getSpeed() == 50);
+			System.out.println(aircraft.canFly() == true);
+			// acceleration
+			System.out.println(aircraft.accelerate(10) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 70);
+			System.out.println(aircraft.getSpeed() == 70);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 90);
+			System.out.println(aircraft.getSpeed() == 90);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 100);
+			System.out.println(aircraft.getSpeed() == 100);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			// deceleration
+			System.out.println(aircraft.accelerate(-20) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 40);
+			System.out.println(aircraft.getSpeed() == 40);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 20);
+			System.out.println(aircraft.getSpeed() == 20);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 0);
+			System.out.println(aircraft.getSpeed() == 0);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+		} catch (Exception e) {
+			System.out.println("Error uncaught exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question4/BadAltitudeSetting.java b/assignment5/Question4/BadAltitudeSetting.java
new file mode 100644
index 0000000..c2a1506
--- /dev/null
+++ b/assignment5/Question4/BadAltitudeSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadAltitudeSetting class is used to test the speed of the program.
+ */
+public class BadAltitudeSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadAltitudeSetting.class.getName().hashCode();
+
+	public BadAltitudeSetting() {
+		super();
+	}
+
+	public BadAltitudeSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question4/BadSpeedSetting.java b/assignment5/Question4/BadSpeedSetting.java
new file mode 100644
index 0000000..2a08413
--- /dev/null
+++ b/assignment5/Question4/BadSpeedSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadSpeedSetting class is used to test the speed of the program.
+ */
+public class BadSpeedSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadSpeedSetting.class.getName().hashCode();
+
+	public BadSpeedSetting() {
+		super();
+	}
+
+	public BadSpeedSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question4/Car.java b/assignment5/Question4/Car.java
new file mode 100644
index 0000000..7017ab2
--- /dev/null
+++ b/assignment5/Question4/Car.java
@@ -0,0 +1,130 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Car class
+ */
+
+public class Car extends Vehicle {
+
+	/**
+	 * Car can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit The speed limit of the car.
+	 * @param speed      the speed of the car.
+	 * @thorws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *         is greater than the speed limit.
+	 */
+	public Car(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Constructor. Default speed limit is 120.
+	 *
+	 * @param speed the speed of the car.
+	 * @thorws BadSpeedSetting if speed is negative. Or if the speed is greater than
+	 *         the speed limit 120.
+	 */
+	public Car(int speed) throws BadSpeedSetting {
+		this(120, speed);
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testCar() {
+		try {
+			Car c1;
+			try {
+				c1 = new Car(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, 121);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			c1 = new Car(120, 100);
+			System.out.println(c1.getSpeed() == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 110);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 120);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c1.accelerate(-20) == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 80);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 60);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 40);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 20);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 0);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Car c2 = new Car(100);
+			System.out.println(c2.getSpeed() == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 110);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 120);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c2.accelerate(-20) == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 80);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 60);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 40);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 20);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 0);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error uncatched exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question4/ExceedSpeedLimit.java b/assignment5/Question4/ExceedSpeedLimit.java
new file mode 100644
index 0000000..ce76da8
--- /dev/null
+++ b/assignment5/Question4/ExceedSpeedLimit.java
@@ -0,0 +1,15 @@
+/*
+ * The ExceedSpeedLimit class is used to check if the speed limit is exceeded
+ */
+public class ExceedSpeedLimit extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = ExceedSpeedLimit.class.getName().hashCode();
+
+	public ExceedSpeedLimit() {
+		super();
+	}
+
+	public ExceedSpeedLimit(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question4/Movable.java b/assignment5/Question4/Movable.java
new file mode 100644
index 0000000..4632969
--- /dev/null
+++ b/assignment5/Question4/Movable.java
@@ -0,0 +1,9 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is a moveable interface.
+ */
+
+public interface Movable {
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed, TrainSpeedChange;
+}
diff --git a/assignment5/Question4/NotEnoughSpeed.java b/assignment5/Question4/NotEnoughSpeed.java
new file mode 100644
index 0000000..b864e1f
--- /dev/null
+++ b/assignment5/Question4/NotEnoughSpeed.java
@@ -0,0 +1,15 @@
+/*
+ * The NotEnoughSpeed class is used to test the speed of the program.
+ */
+public class NotEnoughSpeed extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = NotEnoughSpeed.class.getName().hashCode();
+
+	public NotEnoughSpeed() {
+		super();
+	}
+
+	public NotEnoughSpeed(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question4/Start.java b/assignment5/Question4/Start.java
new file mode 100644
index 0000000..8cc7e46
--- /dev/null
+++ b/assignment5/Question4/Start.java
@@ -0,0 +1,8 @@
+public class Start {
+	public static void main(String[] args) {
+		Vehicle.testVehicle();
+		Car.testCar();
+		Aircraft.testAircraft();
+		Train.testTrain();
+	}
+}
diff --git a/assignment5/Question4/Train.java b/assignment5/Question4/Train.java
new file mode 100644
index 0000000..38c6319
--- /dev/null
+++ b/assignment5/Question4/Train.java
@@ -0,0 +1,71 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Train class inherited from Vehicle class
+ */
+
+public class Train extends Vehicle {
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the train
+	 * @param speed the speed of the train
+	 * @throws BadSpeedSetting
+	 */
+	public Train(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Train can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Tain speed can not be changed.
+	 *
+	 * @throws TrainSpeedChange
+	 */
+	@Override
+	public int accelerate(int amount) throws TrainSpeedChange {
+		throw new TrainSpeedChange("Do not try to accelerate or decelerate the train!");
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testTrain() {
+		try {
+			Train train;
+			try {
+				train = new Train(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				train = new Train(100, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				train = new Train(100, 101);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			train = new Train(100, 50);
+			System.out.println(train.getSpeed() == 50);
+			try {
+				train.accelerate(1);
+			} catch (TrainSpeedChange e) {
+				System.out.println(e.getMessage().equals("Do not try to accelerate or decelerate the train!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: uncaught exception " + e.getClass() + ": " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question4/TrainSpeedChange.java b/assignment5/Question4/TrainSpeedChange.java
new file mode 100644
index 0000000..b72bfd6
--- /dev/null
+++ b/assignment5/Question4/TrainSpeedChange.java
@@ -0,0 +1,15 @@
+/*
+ * The TrainSpeedChange class is used to test the speed of the program.
+ */
+public class TrainSpeedChange extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = TrainSpeedChange.class.getName().hashCode();
+
+	public TrainSpeedChange() {
+		super();
+	}
+
+	public TrainSpeedChange(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question4/Vehicle.java b/assignment5/Question4/Vehicle.java
new file mode 100644
index 0000000..838f478
--- /dev/null
+++ b/assignment5/Question4/Vehicle.java
@@ -0,0 +1,180 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is the abstract Vehicle class.
+ */
+
+public abstract class Vehicle implements Movable {
+	private int speedLimit;
+	private int speed;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the vehicle
+	 * @param speed      the speed of the vehicle
+	 * @throws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *                         is greater than speed limit.
+	 */
+	public Vehicle(int speedLimit, int speed) throws BadSpeedSetting {
+		if (speedLimit < 0 || speed < 0) {
+			throw new BadSpeedSetting("Speed cannot be negative!");
+		}
+		if (speed > speedLimit) {
+			throw new BadSpeedSetting("Speed cannot be greater than speed limit!");
+		}
+		this.speedLimit = speedLimit;
+		this.speed = speed;
+	}
+
+	/**
+	 * Getter of speed.
+	 *
+	 * @return the speed of the vehicle
+	 */
+	public int getSpeed() {
+		return speed;
+	}
+
+	/**
+	 * Accelerate the vehicle.
+	 *
+	 * @param amount the amount of acceleration.
+	 * @throws ExceedSpeedLimit if the speed is greater than speed limit after
+	 *                          increased.
+	 * @thorws NotEnoughSpeed if the speed is less than 0 after decreased.
+	 * @return the new speed of the vehicle
+	 */
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed, TrainSpeedChange {
+		int newSpeed = speed + amount;
+		if (newSpeed > speedLimit) {
+			throw new ExceedSpeedLimit(
+					String.format("Current speed is %d. Accelerate %d will exceed the speed limit!",
+							speed, amount));
+		}
+		if (newSpeed < 0) {
+			throw new NotEnoughSpeed(
+					String.format("Current speed is %d, not enough speed to decelerate!", speed));
+		}
+		speed = newSpeed;
+		return speed;
+	}
+
+	/**
+	 * Whether the vehicle can fly or not.
+	 *
+	 * @return whether the vehicle can fly.
+	 */
+	public abstract boolean canFly();
+
+	/**
+	 * Test.
+	 */
+	public static void testVehicle() {
+		try {
+			Vehicle car;
+			try {
+				car = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				car = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			car = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return false;
+				}
+			};
+			System.out.println(car.getSpeed() == 50);
+			System.out.println(car.canFly() == false);
+			System.out.println(car.accelerate(10) == 60);
+			System.out.println(car.accelerate(10) == 70);
+			System.out.println(car.accelerate(10) == 80);
+			System.out.println(car.accelerate(10) == 90);
+			System.out.println(car.accelerate(10) == 100);
+			try {
+				System.out.println(car.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(car.accelerate(-50) == 50);
+			System.out.println(car.accelerate(-50) == 0);
+			try {
+				System.out.println(car.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Vehicle plane;
+			try {
+				plane = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				plane = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			plane = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return true;
+				}
+			};
+			System.out.println(plane.getSpeed() == 50);
+			System.out.println(plane.canFly() == true);
+			System.out.println(plane.accelerate(10) == 60);
+			System.out.println(plane.accelerate(10) == 70);
+			System.out.println(plane.accelerate(10) == 80);
+			System.out.println(plane.accelerate(10) == 90);
+			System.out.println(plane.accelerate(10) == 100);
+			try {
+				System.out.println(plane.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(plane.accelerate(-50) == 50);
+			System.out.println(plane.accelerate(-50) == 0);
+			try {
+				System.out.println(plane.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: Uncatched exception!");
+		}
+	}
+}
diff --git a/assignment5/Question5/Aircraft.java b/assignment5/Question5/Aircraft.java
new file mode 100644
index 0000000..c234253
--- /dev/null
+++ b/assignment5/Question5/Aircraft.java
@@ -0,0 +1,127 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Aircraft.java inherited from Vehicle class
+ */
+
+public class Aircraft extends Vehicle {
+	/**
+	 * The altitude at which the aircraft is flying.
+	 */
+	private int altitude;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the aircraft
+	 * @param speed      the speed of the aircraft
+	 * @param altitude   the altitude of the aircraft
+	 * @throws BadSpeedSetting    if the speed limit is negative
+	 * @throws BadAltitudeSetting if the altitude is negative
+	 */
+	public Aircraft(int speedLimit, int speed, int altitude) throws BadSpeedSetting, BadAltitudeSetting {
+		super(speedLimit, speed);
+		if (altitude < 0) {
+			throw new BadAltitudeSetting("Altitude cannot be negative!");
+		}
+		this.altitude = altitude;
+	}
+
+	/**
+	 * Getter of altitude.
+	 *
+	 * @return the altitude of the aircraft
+	 */
+	public int getAltitude() {
+		return altitude;
+	}
+
+	/**
+	 * Aircraft can fly.
+	 *
+	 * @return true
+	 */
+	@Override
+	public boolean canFly() {
+		return true;
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testAircraft() {
+		try {
+			Aircraft aircraft;
+
+			try {
+				aircraft = new Aircraft(-10, 10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, -10, 10);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+
+			try {
+				aircraft = new Aircraft(10, 10, -10);
+			} catch (BadAltitudeSetting e) {
+				System.out.println(e.getMessage().equals("Altitude cannot be negative!"));
+			}
+
+			aircraft = new Aircraft(100, 50, 3900);
+			System.out.println(aircraft.getAltitude() == 3900);
+			System.out.println(aircraft.getSpeed() == 50);
+			System.out.println(aircraft.canFly() == true);
+			// acceleration
+			System.out.println(aircraft.accelerate(10) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 70);
+			System.out.println(aircraft.getSpeed() == 70);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 90);
+			System.out.println(aircraft.getSpeed() == 90);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(10) == 100);
+			System.out.println(aircraft.getSpeed() == 100);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			// deceleration
+			System.out.println(aircraft.accelerate(-20) == 80);
+			System.out.println(aircraft.getSpeed() == 80);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 60);
+			System.out.println(aircraft.getSpeed() == 60);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 40);
+			System.out.println(aircraft.getSpeed() == 40);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 20);
+			System.out.println(aircraft.getSpeed() == 20);
+			System.out.println(aircraft.canFly() == true);
+			System.out.println(aircraft.accelerate(-20) == 0);
+			System.out.println(aircraft.getSpeed() == 0);
+			System.out.println(aircraft.canFly() == true);
+			try {
+				aircraft.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+		} catch (Exception e) {
+			System.out.println("Error uncaught exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question5/BadAltitudeSetting.java b/assignment5/Question5/BadAltitudeSetting.java
new file mode 100644
index 0000000..c2a1506
--- /dev/null
+++ b/assignment5/Question5/BadAltitudeSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadAltitudeSetting class is used to test the speed of the program.
+ */
+public class BadAltitudeSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadAltitudeSetting.class.getName().hashCode();
+
+	public BadAltitudeSetting() {
+		super();
+	}
+
+	public BadAltitudeSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question5/BadSpeedSetting.java b/assignment5/Question5/BadSpeedSetting.java
new file mode 100644
index 0000000..2a08413
--- /dev/null
+++ b/assignment5/Question5/BadSpeedSetting.java
@@ -0,0 +1,15 @@
+/*
+ * The BadSpeedSetting class is used to test the speed of the program.
+ */
+public class BadSpeedSetting extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = BadSpeedSetting.class.getName().hashCode();
+
+	public BadSpeedSetting() {
+		super();
+	}
+
+	public BadSpeedSetting(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question5/Car.java b/assignment5/Question5/Car.java
new file mode 100644
index 0000000..7017ab2
--- /dev/null
+++ b/assignment5/Question5/Car.java
@@ -0,0 +1,130 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Car class
+ */
+
+public class Car extends Vehicle {
+
+	/**
+	 * Car can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit The speed limit of the car.
+	 * @param speed      the speed of the car.
+	 * @thorws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *         is greater than the speed limit.
+	 */
+	public Car(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Constructor. Default speed limit is 120.
+	 *
+	 * @param speed the speed of the car.
+	 * @thorws BadSpeedSetting if speed is negative. Or if the speed is greater than
+	 *         the speed limit 120.
+	 */
+	public Car(int speed) throws BadSpeedSetting {
+		this(120, speed);
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testCar() {
+		try {
+			Car c1;
+			try {
+				c1 = new Car(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				c1 = new Car(120, 121);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			c1 = new Car(120, 100);
+			System.out.println(c1.getSpeed() == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 110);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(10) == 120);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c1.accelerate(-20) == 100);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 80);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 60);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 40);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 20);
+			System.out.println(c1.canFly() == false);
+			System.out.println(c1.accelerate(-20) == 0);
+			System.out.println(c1.canFly() == false);
+			try {
+				c1.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Car c2 = new Car(100);
+			System.out.println(c2.getSpeed() == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 110);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(10) == 120);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(10);
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 120. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(c2.accelerate(-20) == 100);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 80);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 60);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 40);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 20);
+			System.out.println(c2.canFly() == false);
+			System.out.println(c2.accelerate(-20) == 0);
+			System.out.println(c2.canFly() == false);
+			try {
+				c2.accelerate(-20);
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error uncatched exception: " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question5/ExceedSpeedLimit.java b/assignment5/Question5/ExceedSpeedLimit.java
new file mode 100644
index 0000000..ce76da8
--- /dev/null
+++ b/assignment5/Question5/ExceedSpeedLimit.java
@@ -0,0 +1,15 @@
+/*
+ * The ExceedSpeedLimit class is used to check if the speed limit is exceeded
+ */
+public class ExceedSpeedLimit extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = ExceedSpeedLimit.class.getName().hashCode();
+
+	public ExceedSpeedLimit() {
+		super();
+	}
+
+	public ExceedSpeedLimit(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question5/ManyVehicles.java b/assignment5/Question5/ManyVehicles.java
new file mode 100644
index 0000000..316e9d6
--- /dev/null
+++ b/assignment5/Question5/ManyVehicles.java
@@ -0,0 +1,58 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: ManyVehicles class manipulate many vehicles
+ */
+
+import java.util.ArrayList;
+
+public class ManyVehicles {
+	private ArrayList<Vehicle> vehicles;
+
+	/**
+	 * Constructor.
+	 */
+	public ManyVehicles() {
+		// initialise instance variables
+		vehicles = new ArrayList<Vehicle>();
+	}
+
+	/**
+	 * Add any kind of vehicle to the arraylist.
+	 *
+	 * @param v the vehicle to be added
+	 */
+	public void addVehicle(Vehicle v) {
+		vehicles.add(v);
+	}
+
+	/**
+	 * Calculate the avergae speed of all vehicles.
+	 *
+	 * @return the average speed of all vehicles
+	 */
+	public double averageSpeed() {
+		double totalSpeed = 0;
+		for (Vehicle v : vehicles) {
+			totalSpeed += v.getSpeed();
+		}
+		return totalSpeed / vehicles.size();
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testManyVehicles() {
+		try {
+			ManyVehicles mv = new ManyVehicles();
+			mv.addVehicle(new Car(100, 100));
+			mv.addVehicle(new Car(90));
+			mv.addVehicle(new Aircraft(100, 70, 3900));
+			mv.addVehicle(new Train(100, 60));
+
+			System.out.println(mv.averageSpeed() == 80.0);
+		} catch (Exception e) {
+			System.out.println("Error uncaught exception: " + e.getClass().getName() + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question5/Movable.java b/assignment5/Question5/Movable.java
new file mode 100644
index 0000000..4632969
--- /dev/null
+++ b/assignment5/Question5/Movable.java
@@ -0,0 +1,9 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is a moveable interface.
+ */
+
+public interface Movable {
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed, TrainSpeedChange;
+}
diff --git a/assignment5/Question5/NotEnoughSpeed.java b/assignment5/Question5/NotEnoughSpeed.java
new file mode 100644
index 0000000..b864e1f
--- /dev/null
+++ b/assignment5/Question5/NotEnoughSpeed.java
@@ -0,0 +1,15 @@
+/*
+ * The NotEnoughSpeed class is used to test the speed of the program.
+ */
+public class NotEnoughSpeed extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = NotEnoughSpeed.class.getName().hashCode();
+
+	public NotEnoughSpeed() {
+		super();
+	}
+
+	public NotEnoughSpeed(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question5/Start.java b/assignment5/Question5/Start.java
new file mode 100644
index 0000000..bc803e0
--- /dev/null
+++ b/assignment5/Question5/Start.java
@@ -0,0 +1,9 @@
+public class Start {
+	public static void main(String[] args) {
+		Vehicle.testVehicle();
+		Car.testCar();
+		Aircraft.testAircraft();
+		Train.testTrain();
+		ManyVehicles.testManyVehicles();
+	}
+}
diff --git a/assignment5/Question5/Train.java b/assignment5/Question5/Train.java
new file mode 100644
index 0000000..38c6319
--- /dev/null
+++ b/assignment5/Question5/Train.java
@@ -0,0 +1,71 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: Train class inherited from Vehicle class
+ */
+
+public class Train extends Vehicle {
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the train
+	 * @param speed the speed of the train
+	 * @throws BadSpeedSetting
+	 */
+	public Train(int speedLimit, int speed) throws BadSpeedSetting {
+		super(speedLimit, speed);
+	}
+
+	/**
+	 * Train can not fly.
+	 *
+	 * @return false
+	 */
+	@Override
+	public boolean canFly() {
+		return false;
+	}
+
+	/**
+	 * Tain speed can not be changed.
+	 *
+	 * @throws TrainSpeedChange
+	 */
+	@Override
+	public int accelerate(int amount) throws TrainSpeedChange {
+		throw new TrainSpeedChange("Do not try to accelerate or decelerate the train!");
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testTrain() {
+		try {
+			Train train;
+			try {
+				train = new Train(-1, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				train = new Train(100, -1);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				train = new Train(100, 101);
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			train = new Train(100, 50);
+			System.out.println(train.getSpeed() == 50);
+			try {
+				train.accelerate(1);
+			} catch (TrainSpeedChange e) {
+				System.out.println(e.getMessage().equals("Do not try to accelerate or decelerate the train!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: uncaught exception " + e.getClass() + ": " + e.getMessage());
+		}
+	}
+}
diff --git a/assignment5/Question5/TrainSpeedChange.java b/assignment5/Question5/TrainSpeedChange.java
new file mode 100644
index 0000000..b72bfd6
--- /dev/null
+++ b/assignment5/Question5/TrainSpeedChange.java
@@ -0,0 +1,15 @@
+/*
+ * The TrainSpeedChange class is used to test the speed of the program.
+ */
+public class TrainSpeedChange extends Exception {
+	// generate serial ID by class name
+	private static final long serialVersionUID = TrainSpeedChange.class.getName().hashCode();
+
+	public TrainSpeedChange() {
+		super();
+	}
+
+	public TrainSpeedChange(String message) {
+		super(message);
+	}
+}
diff --git a/assignment5/Question5/Vehicle.java b/assignment5/Question5/Vehicle.java
new file mode 100644
index 0000000..838f478
--- /dev/null
+++ b/assignment5/Question5/Vehicle.java
@@ -0,0 +1,180 @@
+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-24
+ * Description: This is the abstract Vehicle class.
+ */
+
+public abstract class Vehicle implements Movable {
+	private int speedLimit;
+	private int speed;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param speedLimit the speed limit of the vehicle
+	 * @param speed      the speed of the vehicle
+	 * @throws BadSpeedSetting if speedLimit or speed is negative. Or if the speed
+	 *                         is greater than speed limit.
+	 */
+	public Vehicle(int speedLimit, int speed) throws BadSpeedSetting {
+		if (speedLimit < 0 || speed < 0) {
+			throw new BadSpeedSetting("Speed cannot be negative!");
+		}
+		if (speed > speedLimit) {
+			throw new BadSpeedSetting("Speed cannot be greater than speed limit!");
+		}
+		this.speedLimit = speedLimit;
+		this.speed = speed;
+	}
+
+	/**
+	 * Getter of speed.
+	 *
+	 * @return the speed of the vehicle
+	 */
+	public int getSpeed() {
+		return speed;
+	}
+
+	/**
+	 * Accelerate the vehicle.
+	 *
+	 * @param amount the amount of acceleration.
+	 * @throws ExceedSpeedLimit if the speed is greater than speed limit after
+	 *                          increased.
+	 * @thorws NotEnoughSpeed if the speed is less than 0 after decreased.
+	 * @return the new speed of the vehicle
+	 */
+	public int accelerate(int amount) throws ExceedSpeedLimit, NotEnoughSpeed, TrainSpeedChange {
+		int newSpeed = speed + amount;
+		if (newSpeed > speedLimit) {
+			throw new ExceedSpeedLimit(
+					String.format("Current speed is %d. Accelerate %d will exceed the speed limit!",
+							speed, amount));
+		}
+		if (newSpeed < 0) {
+			throw new NotEnoughSpeed(
+					String.format("Current speed is %d, not enough speed to decelerate!", speed));
+		}
+		speed = newSpeed;
+		return speed;
+	}
+
+	/**
+	 * Whether the vehicle can fly or not.
+	 *
+	 * @return whether the vehicle can fly.
+	 */
+	public abstract boolean canFly();
+
+	/**
+	 * Test.
+	 */
+	public static void testVehicle() {
+		try {
+			Vehicle car;
+			try {
+				car = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				car = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return false;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			car = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return false;
+				}
+			};
+			System.out.println(car.getSpeed() == 50);
+			System.out.println(car.canFly() == false);
+			System.out.println(car.accelerate(10) == 60);
+			System.out.println(car.accelerate(10) == 70);
+			System.out.println(car.accelerate(10) == 80);
+			System.out.println(car.accelerate(10) == 90);
+			System.out.println(car.accelerate(10) == 100);
+			try {
+				System.out.println(car.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(car.accelerate(-50) == 50);
+			System.out.println(car.accelerate(-50) == 0);
+			try {
+				System.out.println(car.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+
+			Vehicle plane;
+			try {
+				plane = new Vehicle(-10, -20) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be negative!"));
+			}
+			try {
+				plane = new Vehicle(0, 50) {
+					@Override
+					public boolean canFly() {
+						return true;
+					}
+				};
+			} catch (BadSpeedSetting e) {
+				System.out.println(e.getMessage().equals("Speed cannot be greater than speed limit!"));
+			}
+			plane = new Vehicle(100, 50) {
+				@Override
+				public boolean canFly() {
+					return true;
+				}
+			};
+			System.out.println(plane.getSpeed() == 50);
+			System.out.println(plane.canFly() == true);
+			System.out.println(plane.accelerate(10) == 60);
+			System.out.println(plane.accelerate(10) == 70);
+			System.out.println(plane.accelerate(10) == 80);
+			System.out.println(plane.accelerate(10) == 90);
+			System.out.println(plane.accelerate(10) == 100);
+			try {
+				System.out.println(plane.accelerate(10) == 110);
+				System.out.println("Error: ExceedSpeedLimit should be thrown!");
+			} catch (ExceedSpeedLimit e) {
+				System.out.println(e.getMessage().equals(
+						"Current speed is 100. Accelerate 10 will exceed the speed limit!"));
+			}
+			System.out.println(plane.accelerate(-50) == 50);
+			System.out.println(plane.accelerate(-50) == 0);
+			try {
+				System.out.println(plane.accelerate(-50) == -50);
+				System.out.println("Error: NotEnoughSpeed should be thrown!");
+			} catch (NotEnoughSpeed e) {
+				System.out.println(e.getMessage()
+						.equals("Current speed is 0, not enough speed to decelerate!"));
+			}
+		} catch (Exception e) {
+			System.out.println("Error: Uncatched exception!");
+		}
+	}
+}