Test : Java_3

This test contains 10 questions based on Java.
Each question answered correctly awards you 1 point and each incorrect answer has a penalty of -0.25 points, no points are deducted for unattempted answers.

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You Get +1 for each correct answer and -0.25 for each incorrect answer

Time Left - minutes :seconds

Which of these lines will give an error line 1 :int a=1; line 2 :char c=25; line 3 :double d=2.9;

line 1	line 2
line 3	none of these

D

no error since character can take integer value

Following code prints ?

1. int a=5;  
2. System.out.println(a -= a+ = a -= a += a);  

0	5
-5	none of these

B

It is evaluated as a -= (a += ( a -= (a += 5) )) a -= (a += ( a -= 10 )) The value of a is still 5 a -= (a += -5 ) a -= 0 which is 5

If a class inheriting an abstract class does not define all of its function then it will be known as?

abstract	A simple class
Static class	None of the mentioned

A

What is the output of this program?

 class A {
        public int i;
        private int j;
    }    
    class B extends A {
        void display() {
            super.j = super.i + 1;
            System.out.println(super.i + " " + super.j);
        }
    }    
    class inheritance {
        public static void main(String args[])
        {
            B obj = new B();
            obj.i=1;
            obj.j=2;   
            obj.display();     
        }
   }

2 2	2 3
Runtime Error	Compilation Error

D

public class Test2 
{
    public static int x;
    public static int foo(int y) 
    {
        return y * 2;
    }
    public static void main(String [] args) 
    {
        int z = 5;
        assert z > 0; /* Line 11 */
        assert z > 2: foo(z); /* Line 12 */
        if ( z < 7 )
            assert z > 4; /* Line 14 */

        switch (z) 
        {
            case 4: System.out.println("4 ");
            case 5: System.out.println("5 ");
            default: assert z < 10;
        }

        if ( z < 10 )
            assert z > 4: z++; /* Line 22 */
        System.out.println(z);
    }
}

Line 11	Line 12
Line 14	Line 22

D

Assert statements should not cause side effects. Line 22 changes the value of z if the assert statement is false. Option A is fine; a second expression in an assert statement is not required. Option B is fine because it is perfectly acceptable to call a method with the second expression of an assert statement. Option C is fine because it is proper to call an assert statement conditionally.

What is the biggest disadvantage of using inheritance

Can be implemented in point class	Pointers can't be used
Multiple inheritance can't be used	None of the above

C

When a class extends an abstract class, it can?t extend any other class.

Consider the following two classes:

public class ClassA {
    public void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public static void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}

public class ClassB extends ClassA {
    public static void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}

Which method hides a method in the superclass?

MethodOne	MethodTwo
MethodThree	MethodFour

D

What is the output of this program?

 import java.util.*;
    class stack {
        public static void main(String args[]) {
            Stack obj = new Stack();
            obj.push(new Integer(3));
            obj.push(new Integer(2));
            obj.pop();
            obj.push(new Integer(5));
          System.out.println(obj);
        }
    }

[3, 5]	[3, 2]
[3, 2, 5]	[3, 5, 2]

A

push() and pop() are standard functions of the class stack, push() inserts in the stack and pop removes from the stack. 3 & 2 are inserted using push() the pop() is used which removes 2 from the stack then again push is used to insert 5 hence stack contains elements 3 & 5. Output: $ javac stack.java $ java stack [3, 5]

Which of these can be used to fully abstract a class from its implementation?

Objects	Packages
Interfaces	None of the Mentioned.

C

what will be the output int i=10; System.out.println(i++ + ++i);

20	21
22	23

C

i++ will first use the value and then increment it by one, ++i will increment value first Therefore i++ + ++i= 10 + 12 =22

Finish Test