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.

[ Java ]

Which of the following statements is true?

An abstract class can declare a static abstract method

An abstract class can have abstract private methods

All methods in an Abstract class need to be abstract

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

2.

[ Java ]

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.

class will not compile

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

Extend this class and make contructor public

3.

[ Java ]

When is an object's finalize method called?

When System.gc() is called

When the object needs to release any resource it holds

Right before the object is garbage collected

When last reference to object is destroyed or out of scope

4.

[ Java ]

Which of the following code snippets will compile?

List a = new ArrayList();

List a = new ArrayList();

List a = new ArrayList();

None of the snippets will compile

5.

[ Java ]

Which Java class provides variables local to each thread?

ThreadLocal

Thread

LocalThread

Runnable

6.

[ Java ]

What is the command to run a JAR file application?

$ java -start application.jar

$ java -run application.jar

$ java -jar application.jar

$ jar -java application.jar

7.

[ Java ]

Which one these is a valid keyword in Java?

unsigned

string

Float

interface

8.

[ Java ]

Which member of an abstract class can be abstract?

Private methods

Static methods

Protected methods

Constructors

9.

[ Java ]

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

Element is added successfully

Element is not added and add() method returns false

Compile time error

IllegalStateException

10.

[ Java ]

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

11.

[ Java ]

Which of the following declaration is correct?

class A implements InterfaceA extends ClassA

class A extends ClassA, ClassB implements InterfaceA, InterfaceB

class A implements InterfaceA, InterfaceB extends ClassA

class A extends ClassB implements InterfaceA, InterfaceB

12.

[ Java ]

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

long

integer

float

double

13.

[ Java ]

What is @Override annotation?

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

It makes the method virtual

It forces the subclass to override the method

It stops overriding the method

14.

[ Java ]

Which of the following code snippets would compile successfully?

int i = 1L + 2;

int i = 1L + 2L;

float = 3.14;

long l = 1L + 2;

15.

[ Java ]

Which Java declaration will return syntax error?

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

List>var;

List var;

float var = 4.3f;

16.

[ Java ]

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

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

Only class Audi and subclasses of Audi within any package

Only class Audi

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

17.

[ Java ]

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");
     }
}

Not Equal

Equal

Compile-Time Error

Syntax Error

18.

[ Java ]

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

default

protected

public

private

19.

[ Java ]

What is the difference between Vector and ArrayList?

ArrayList uses Array as its data structure but Vector used vector

Vector is dynamically resized but ArrayList is manually resized

Vector is synchronized but ArrayList is not

ArrayList is synchronized but Vector is not

20.

[ Java ]

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());
   }
}

x

compile time error

run time error

5

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