Java Quiz1 Basics and OOPS

Predict the output:

int arr[ ] = new int[5];

System.out.println(arr[1]);

• 1
• 0
• null
• garbage value

Predict the output:

package main;

class Main {

public static void main(String args[]) {

int t;

System.out.println(t); } }

• 0
• Garbage Value
• complie time error
• runtime error

public class Main {

public static void main(String args[]) {

int arr[] = {10, 20, 30, 40, 50};

for(int i=0; i < arr.length; i++) {

System.out.print(" " + arr[i]);

} } }

• 10 20 30 40 50
• 10 20 30 40
• complie time error
• runtime error

Which of the following is the immediate parent class for Integer, Float and Long classes?

• Object Class
• Wrapper Class
• Number Class
• none of the above

predict the output:

abstract class Sample{ //Line0

public int a; //Line1

demo(){ //Line2

a=10; //Line3

} }

• Line0 : abstract class must be public
• Line1: abstract class cannot have instace variables
• Line2: demo() Return type for the method is missing
• Line3: Illegal initialization

predict the output: abstract class Sample{

Sample(){

super(); //Line1

}

abstract final public get(); //Line2

public static void check() { //Line3

System.out.println("Static checking"); } }

• Line1: abstract class cannot call super
• Line2:Cannot pair abstract final
• Line3: abstract class cannot have static methods
• all 3 lines are with compile time error

Predict the output:

abstract class Sample{

Sample(){

super(); //Line1

}

public final void get() { //Line2

System.out.println(); }

public static abstract void check(); //Line3

}

• Line1: abstract class cannot call super
• Line2: abstract class cannot have final method
• Line3: static and abstract cannot be paired
• all 3 lines are with compile time error

Predict the output:

public class Test {

public static void main(String[] args) {

static int x = 10;//Line1

System.out.println(x);//Line2 } }

• prints out 10
• Line1: compile time error: illegal modifiers (static )
• Line 2: compile time error: static variable x maynot be used in static context
• Line2: runtime error; x illegal usage

Predict the output:

Find Compile Time error at

public class Test {

final int t1; //Line1

public final Test() { //Line2

t1 = 10;

System.out.println("Test Created"); }

public static void main(String[] args) {

Test t = new Test(); //Line3

System.out.println(t.t1); //Line4

} }

• Line1: final variable not initialized
• Line2: illegal modifier final for constrctor
• Line3: Object cannot be created for constructors with final modifiers
• Line4: non initialized final variable cannot be accessed

Identify the lines that can be replaced at /*Insert code here.*/ in the given code to display 100 successfully:

interface Testable{

int testValue=100; }

public class Test implements Testable{

public static void main(String[] args) {

int result = /*Insert code here */;

System.out.println(result); } }

1. Testable.testValue; 2. testValue; 3. Test.testValue; 4. new Test().testValue;

• 1,2,3,4
• 1,3,4
• 1,3
• 1