Question

For Questions 1-3: consider the following code:

public class A

{

private int number;

protected String name;

public double price;

public A()

{

System.out.println(“A() called”);

}

private void foo1()

{

System.out.println(“A version of foo1() called”);

}

protected int foo2()

{

Sysem.out.println(“A version of foo2() called);

return number;

}

public String foo3()

{

System.out.println(“A version of foo3() called”);

Return “Hi”;

}

}//end class A

public class B extends A

{

private char service;

public B()

{

  super();

  System.out.println(“B() called”);

}

public void foo1()

{

System.out.println(“B version of foo1() called”);

}

protected int foo2()

{

int n = super.foo2();

System.out.println(“B version of foo2() called”);

return (n+5);

}

public String foo3()

{

String temp = super.foo3();

System.out.println(“B version of foo3()”);

return (temp+” foo3”);

}

}//end class B

public class C extends B

{

public C()

{

super();

System.out.println();

}

public void foo1()

{

System.out.println(“C version of foo1() called”);

}

}//end class C

Assignment

1. (20 pts) What is the output of this code sequence?

B b1 = new B();

2. (20 pts) What is the output of this code sequence?

B b3 = new B();

int n = b3.foo2();

3. (20 pts) What is the output of the following code?

//b4 is a B object reference

System.out.println(b4.foo3());

4. (40 pts) You coded the following class:

public class N extends String, Integer

{

}

When you compile, you get the following message:

N.java:1: ‘{‘ expected

public class N extends String, Integer

                                              ^

1 error

Explain what the problem is and how to fix it.

Answer 1

B b1 = new B();

will call the B class constructor and before executing that it will call the A class constructor and prints A() called and comes back to the B class constructor and prints B() called

B b3 = new B();
will call the B class constructor and before executing that it will call the A class constructor and prints A() called and comes back to the B class constructor and prints B() called

it will call foo2() in A and prints A version of foo2() called and returns 0 and comes back to foo2() in B and prints B version of foo2() called returns 5

System.out.println(b4.foo3());

it will call foo3() in class B and from there it will goto class A and prints A version of foo3() called
and returns Hi and backs to foo3() in B and prints B version of foo3() called and returns Hi foo3 prints

public class N extends String, Integer

{

}
In java we can't extend more than one class and String and Integer classes are final we can't extend
Solution:

public class N

{

}