final project q2

finalproject/Question2/IUser.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-25
+ * Description: This is the interface of IUser.
+ */
+
+public interface IUser {
+	public String getName();
+
+	public int getBook();
+
+	public void moreBook(int number);
+}

finalproject/Question2/Lender.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-25
+ * Description: This is the Lender class.
+ */
+
+public class Lender extends User {
+	/**
+	 * Constructor.
+	 *
+	 * @param name The user's name.
+	 * @param book number of bookds lent by the user. This will be store in negetive value.
+	 */
+	public Lender(String name, int book) {
+		// lender negetive book value
+		super(name, -book);
+	}
+
+	/**
+	 * Increases the number of bookds.
+	 *
+	 * @param book the number of books.
+	 */
+	public void moreBook(int book) {
+		setBook(getBook() - book);
+	}
+
+	/**
+	 * Test.
+	 */
+	public static void testLender() {
+		Lender l = new Lender("Anna", 5);
+		System.out.println(l.getName() == "Anna");
+		System.out.println(l.getBook() == -5);
+		l.setBook(-6);
+		System.out.println(l.getBook() == -6);
+		l.moreBook(2);
+		System.out.println(l.getBook() == -8);
+		l.moreBook(-9);
+		System.out.println(l.getBook() == 1);
+	}
+}

finalproject/Question2/Test.java

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+public class Test {
+	public static void main(String[] args) {
+		User.testUser();
+		Lender.testLender();
+	}
+}

finalproject/Question2/User.java

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+/*
+ * Author: CHEN Yongyuan (Walter) 1930006025 from OOP(1007)
+ * Date: 2022-04-25
+ * Description: This is the User class.
+ */
+
+public abstract class User implements IUser {
+	/**
+	 * The user's name.
+	 */
+	private String name;
+
+	/**
+	 * The number of books borrowed by the user.
+	 */
+	private int book;
+
+	/**
+	 * Constructor.
+	 *
+	 * @param name The user's name.
+	 * @param book The number of books borrowed by the user.
+	 */
+	public User(String name, int book) {
+		this.name = name;
+		this.book = book;
+	}
+
+	/**
+	 * Getter of the user's name.
+	 *
+	 * @return The user's name.
+	 */
+	public String getName() {
+		return name;
+	}
+
+	/**
+	 * Getter of the number of books borrowed by the user.
+	 *
+	 * @return The number of books borrowed by the user.
+	 */
+	public int getBook() {
+		return book;
+	}
+
+	/**
+	 * Change the number of books borrowed by the user.
+	 *
+	 * @param book The number of books borrowed by the user.
+	 */
+	protected void setBook(int book) {
+		this.book = book;
+	}
+
+	/**
+	 * Increase the number of books borrowed by the user.
+	 *
+	 * @param book The number of books borrowed by the user.
+	 */
+	public abstract void moreBook(int number);
+
+	/**
+	 * Test.
+	 */
+	public static void testUser() {
+		User user = new User("Walter", 3) {
+			@Override
+			public void moreBook(int number) {
+				setBook(getBook() + number);
+			}
+		};
+		System.out.println(user.getName() == "Walter");
+		System.out.println(user.getBook() == 3);
+		user.moreBook(2);
+		System.out.println(user.getBook() == 5);
+	}
+}