final project q9

finalproject/Question9/Lender.java

@@ -0,0 +1,42 @@
+/*
+ * 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);
+	}
+}