Question

QUESTION 1

1. If we run the following code:

   A a = new A(1);
   B b = new B(2);
   System.out.println(b);

   Select all of the following pieces of code that would compile and run with no errors, printing the value of 1 followed by the value of 2, each on separate lines.

   	A.	public class A {     private int y;     public A(int y) {         this.y = y;     }     public int getY() {         return y;     }     public String toString() {         return "" + y;     } } public class B extends A {     private int x;     public B(int x) {         this.x = x;     }     public String toString() {         return super.toString() + "\n" + x; } }
   	B.	public class A {     private int y;     public A(int y) {         this.y = y;     }     public int getY() {         return y;     }     public String toString() {         return "" + y;     } } public class B extends A {     private int x;     public B(int x) {         this.x = x;     }     public String toString() {         return "" + y + "\n" + x; } }
   	C.	public class A {     protected int y;     public A(int y) {         this.y = y;     }     public int getY() {         return y;     }     public String toString() {         return "" + y;     } } public class B extends A {     private int x;     public B(int x) {         this.x = x;     }     public String toString() {         return "" + y + "\n" + x; } }
   	D.	public class A {     private int y;     public A(int y) {         this.y = y;     }     public int getY() {         return y;     }     public String toString() {         return "" + y;     } } public class B extends A {     private int x;     public B(int x) {         this.x = x;     }     public String toString() {         return "" + x + "\n" + super.toString(); } }
   	E.	public class A {     private int y;     public A(int y) {         this.y = y;     }     public int getY() {         return y;     }     public String toString() {         return "" + y;     } } public class B extends A {     private int x;     public B(int x) {         this.x = x;     }     public String toString() {         return "" + getY() + "\n" + x; } }

QUESTION 2

1. Why did you choose the answer you did in Question 1? Explain your thinking as clearly as possible.

Answer 1

1)  None of these

2)
Explanation:
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All of these choices have no default constructor in class A(The constructor which takes no arguments)
In all these choices class B extends class A.
and It is important that the class B's constructor must call the parameterized constructor of class A, because there is no default constructor of class A.
but none of these choices, call the constructor of class A using super keyword in class B's constructor.
That's the reason why none of these options compile correctly.