OOPS Fundamentals

public class Null {

public static boolean greet() {

System.out.print("Program execute = ");

return true;

}

public static void main(String[] args) {

System.out.println(Null.greet());

}

}

• Program execute = true

• Program execute = false

• Program execute = null

• Compilation Error

1. class Test1 {

public static void main(String[] args)

{

int x = 20;

System.out.println(x);

}

static

{

int x = 10;

System.out.print(x + " ");

}

}

• 20 10

• 10 20

• 10 10

• 20 20

class Test1 {

int x = 10;

public

static void main(String[] args)

{

System.out.println(x);

}

static

{

System.out.print(x + " ");

}

}

• 20 10

• 0 10

• error

• 10 10

class SamsungMobile

{

public static void main(String[] args)

{

Simple.getData();

Simple.display();

}

}

class Simple

{

static int a, b = 20;

static void getData()

{

System.out.println("a = " + a);

}

static void display()

{

System.out.println("b = " + b);

}

static

{

System.out.println("Samsung Mobile");

a = 4 * b;

}

}

• Samsung Mobile

  a = 80

  b = 20

• Samsung Mobile

  a = 0

  b = 20

• Samsung Mobile

  a = 20

  b = 0

• Compilation Error

What will be the output of the following program?

 public class Final

{

final int assign = 30;

public static void main(String[] args)

{

final int result = 20;

final int assign;

Final f = new Final();

assign = 20;

System.out.println(assign);

System.out.println(f.assign);

System.out.println(f.process(result));

}

int process(int a)

{

return a + 5;

}

}

• 20

  30

  25

• 20

  20

  25

• 30

  30

  25

• Error

class Output

{

final static short i = 2;

public static int j = 0;

public static void main(String [] args)

{

for (int k = 0; k < 3; k++)

{

switch (k)

{

case i: System.out.print(" 0 ");

case i-1: System.out.print(" 1 ");

case i-2: System.out.print(" 2 ");

}

}

}

}

• 2 1 0 1 0 0

• 0 1 2 1 2 2

• 2 1 2 0 1 2

• 0 1 2

• error

Which of the following classes fail to compile?

class X { }

abstract class Y { }

class Z { abstract void method(); }

• X

• Y

• Z

• All classes compile

What will be the output of the following Java program?

class A

{

int i;

}

class B extends A

{

int j;

void display()

{

super.i = j + 1;

System.out.println(j + " " + i);

}

}

class inheritance

{

public static void main(String args[])

{

B obj = new B();

obj.i=1;

obj.j=2;

obj.display();

}

}

• 3 3

• 2 3

• 2 2

• error

Output of following Java program?

class Base {

public void Print()

{

System.out.println("Base");

}

}

class Derived extends Base

{

public void Print()

{

System.out.println("Derived");

}

}

class Main{

public static void DoPrint(

Base o ) {

o.Print();

}

public static void main(String[]

args) {

Base x =

new Base();

Base y =

new Derived();

Derived z

= new Derived();

DoPrint(x);

DoPrint(y);

DoPrint(z);

}

}

• Base

  Derived

  Derived

• Base

  Base

  Derived

• Base

  Derived

  Base

• Error

Which of these is correct way of inheriting class A by class B?

• class B + class A {}

• class A + class B {}

• Class B extends A {}

• Class A extends B {}