Sun Certified Java Professional (SCJP) 1.5 Question Bank - 22

Given:
1. public class Target {
2.   private int i = 0;
3.   public int addOne(){
4.     return ++i;
5.   }
6. }

And:
1. public class Client {
2.   public static void main(String[] args){
3.     System.out.println(new Target().addOne());
4.   }
5. }
Which change can you make to Target without affecting Client?
A. Line 4 of class Target can be changed to return i++;
B. Line 2 of class Target can be changed to private int i = 1;
C. Line 3 of class Target can be changed to private int addOne(){
D. Line 2 of class Target can be changed to private Integer i = 0;

Given:
10. interface A { void x(); }
11. class B implements A { public void x() {} public void y() {} }
12. class C extends B { public void x() {} }

And:

20. java.util.List<A> list = new java.util.ArrayList<A>();
21. list.add(new B());
22. list.add(new C());
23. for (A a : list) {
24.   a.x();
25.   a.y();
26. }
What is the result?
A. The code runs with no output.
B. An exception is thrown at runtime.
C. Compilation fails because of an error in line 20.
D. Compilation fails because of an error in line 21.
E. Compilation fails because of an error in line 23.
F. Compilation fails because of an error in line 25.

Given:
1. class SuperClass {
2.   public A getA() {
3.     return new A();
4.   }
5. }
6. class SubClass extends SuperClass {
7.   public B getA(){
8.     return new B();
9.   }
10.}
Which statement is true?
A. Compilation will succeed if A extends B.
B. Compilation will succeed if B extends A.
C. Compilation will always fail because of an error in line 7.
D. Compilation will always fail because of an error in line 8.

Given:
10: public class Hello {
11:   String title;
12:   int value;
13:   public Hello() {
14:     title += " World";
15:   }
16:   public Hello(int value) {
17:     this.value = value;
18:     title = "Hello";
19:     Hello();
20:   }
21: }

and:

30: Hello c = new Hello(5);
31: System.out.println(c.title);
What is the result?
A. Hello
B. Hello World
C. Compilation fails.
D. Hello World 5
E. The code runs with no output.
F. An exception is thrown at runtime.

Given:
1. class Pizza {
2.   java.util.ArrayList toppings;
3.   public final void addTopping(String topping) {
4.     toppings.add(topping);
5.   }
6. }
7. public class PepperoniPizza extends Pizza {
8.   public void addTopping(String topping) {
9.     System.out.println("Cannot add Toppings");
10.  }
11.  public static void main(String[] args) {
12.    Pizza pizza = new PepperoniPizza();
13.    pizza.addTopping("Mushrooms");
14.  }
15.}
What is the result?
A. Compilation fails.
B. Cannot add Toppings
C. The code runs with no output.
D. A NullPointerException is thrown in Line 4.

If you've sometime, you can read my other SCJP Question bank articles