CS122/504 QUIZ 2

                                   Prof. Lixin Tao

                                   April 18, 2006

1)  What will be printed if we run the following program? [20%]

        class A {
        	public A() {
        		System.out.println("A()");
        	}
        	public void finalize() {
        		System.out.println("~A()");
        	}
        }
        
        class B extends A {
        	public B() {
        		System.out.println("B()");
        	}
        	public void finalize() {
        		System.out.println("~B()");
        		super.finalize();
        	}
        }
        
        public class ClassConstructors {
        	public static void main(String[] args) {
        		new B();
        		System.gc();
        	}
        }

2)  What will be printed if we run the following program? [20%]

        abstract class Talkable {
        	abstract void talk();
        	void sing() {
        		System.out.println("Talker can sing.");
        	}
        }
        
        class Cat extends Talkable {
        	void talk() {
        		System.out.println("I am a cat.");
        	}
        	
        	void sing() {
        		System.out.println("Cat can sing.");
        	}
        }
        
        class Dog extends Talkable {
        	void talk() {
        		System.out.println("I am a dog.");
        	}
        	
        	void sing() {
        		System.out.println("Dog can sing.");
        	}
        }
        
        public class TestAbstractClass {
        	public static void main(String[] args) {
        		Talkable[] pet = new Talkable[2];
        		pet[0] = new Cat();
        		pet[1] = new Dog();
        		pet[0].talk();
        		pet[1].talk();
        		pet[0].sing();
        		pet[1].sing();
        	}
        }
    

3) What will be printed if we run the following program? [20%]

        class Exception1 extends Exception {}
        class Exception2 extends Exception {}
        class Exception3 extends Exception {}
        
        public class ShowException {
          public static void main(String[] args) {
            for (int i = 1; i<=3; i++) {
              try {
                f(i);
              }
              catch (Exception3 e) {
                System.out.println("main() catched " + e);
              }
            }
          }
        
          static void f(int i) throws Exception3 {
            try {
              if (i == 1)
                throw new Exception1();
              else if (i == 2)
                throw new Exception2();
              else if (i == 3)
                throw new Exception3();
            }
            catch (Exception1 e) {
              System.out.println("f(" + i + ") catched " + e);
            }
            catch (Exception2 e) {
              System.out.println("f(" + i + ") catched " + e);
              throw new Exception3();
            }
            finally {
              System.out.println("f(" + i + ") executes finally block");
            }
          }
        }

4) Design and implement a class Stack of integers with linked Node objects defined below:

        class Node {
          int value;
          Node next;

          public Node(int value, Node next) {
            this.value = value;
            this.next = next;
          }

          public Node() {
            this(0, null);
          }
        }

[40%]