Java Online Quiz

January 29, 2021

Below are the instructions for this quiz:

Time Limit for this Quiz is 30 minutes
This quiz has 20 questions
Multiple choice questions
Multiple attempts are allowed

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1. What happens when we try to add the same element twice to a Set?

IllegalStateException

Compile time error

Element is not added and add() method returns false

Element is added successfully

2. Which one these is a valid keyword in Java?

unsigned

interface

string

Float

3. What is the difference between Vector and ArrayList?

Vector is dynamically resized but ArrayList is manually resized

Vector is synchronized but ArrayList is not

ArrayList uses Array as its data structure but Vector used vector

ArrayList is synchronized but Vector is not

4. Which of the following declaration is correct?

class A implements InterfaceA extends ClassA

class A implements InterfaceA, InterfaceB extends ClassA

class A extends ClassB implements InterfaceA, InterfaceB

class A extends ClassA, ClassB implements InterfaceA, InterfaceB

5. What is @Override annotation?

It causes the compiler to check the method exists in a superclass

It stops overriding the method

It makes the method virtual

It forces the subclass to override the method

6. In the following code. Who has access to member num?package car;
public class Audi {
int num;
}

Class Audi, subclass of Audi defined in package car, and other classes in package car

Only class Audi and subclasses of Audi within any package

Only class Audi

Class Audi, subclasses of Audi defined in any package, and other classes in package car

7. Which Java declaration will return syntax error?

Double[] var = {1.0,2.0,3.0,4.0};

List var;

float var = 4.3f;

List>var;

8. Which of the following code snippets would compile successfully?

int i = 1L + 2L;

long l = 1L + 2;

int i = 1L + 2;

float = 3.14;

9. What modifier is used to provide access to a method within the class and all the extending classes?

protected

public

private

default

10. Which member of an abstract class can be abstract?

Constructors

Static methods

Protected methods

Private methods

11. What is correct variable type for the result?... variable = 5 + 0.11;

integer

double

long

float

12. There is a class with private constructors only. How can we provide a way to create instance of this class?

There is no way to create instance of this class.

Create a static method within the class that will call one of the private contructors

Extend this class and make contructor public

class will not compile

13. Create a set of strings and add the string "def" three times to this set, then remove an "def" string. What will happen when size() method is called on this set?

returns 0

IllegalStateException

compile time error

returns 2

14. What is the output for the below code?public class Test{
public static void main(String[] args){
Integer i = Integer.valueOf("1");
if(i.toString()=="1")
System.out.println("Equal");
else
System.out.println("Not Equal");
}
}

Compile-Time Error

Not Equal

Equal

Syntax Error

15. Which Java class provides variables local to each thread?

ThreadLocal

LocalThread

Thread

Runnable

16. Which of the following code snippets will compile?

List a = new ArrayList();

None of the snippets will compile

17. What is the command to run a JAR file application?

$ java -run application.jar

$ java -start application.jar

$ jar -java application.jar

$ java -jar application.jar

18. When is an object's finalize method called?

When System.gc() is called

Right before the object is garbage collected

When last reference to object is destroyed or out of scope

When the object needs to release any resource it holds

19. Which of the following statements is true?

An abstract class can declare a static abstract method

An abstract class can have abstract private methods

An abstract class can have both abstract and non-abstract methods

All methods in an Abstract class need to be abstract

20. What is the output of the following class?public class Test{
public Test() {
int x = 5;
return x;
}
public static void main(String[] args){
System.out.println(new Test());
}
}

run time error

compile time error