Java Online Test | Know Your Java Knowledge

1. Core Java Online Test

Get free Java online test and prepare yourself for Java exam. This Java online test will help you to test your Java performance. This practice set for Java contains the top 25 Java MCQ, which will help you to boost your confidence. If you find yourself good in Java online test, then prepare yourself to crack Java interview questions by following our Java interview guide.

So, let’s check your Java performance. ALL THE BEST! for Java online test.

Java Online Test | Know Your Java Knowledge

Q.1 Which interface should be implemented for sorting on basis of many criteria’s?

Comparator

Comparable

Serializable

Correct! Wrong!

Q.2 Can two threads on same ConcurrentHashMap object access it concurrently

We need to add additional functionality to achieve the same.

Its not possible

Different threads will access different|completely different} segments concurrently

Correct! Wrong!

Q.3 LinkedHashSet implements:

Set

Cloneable

Serializable

All of the above

Correct! Wrong!

Q.4 What will be the output of the following code -

a followed by exception

a

a
b

Compile time exception

Correct! Wrong!

Q.5 In WeakHashMap

An entry are automatically removed by garbage collector

Behaves normally like HashMap

An entry are never removed by garbage collector

Correct! Wrong!

Q.6 A EnumSet

Can use enum and non enum type keys

Cannot use enum type keys

Is specialised Set implementation for use with enum type keys only

Correct! Wrong!

Q.7 Iterator returned by HashSet is

Fail-fast

Fail-safe

None of the above

Correct! Wrong!

Q.8 Iterator returned by CopyOnWriteArraySet is

Fail-fast

Fail-safe

None of the above

Correct! Wrong!

Q.9 Iterator returned by TreeSet is

Fail-fast

Fail-safe

None of the above

Correct! Wrong!

Q.10 Iterator returned by LinkedHashSet is

Fail-fast

Fail-safe

None of the above

Correct! Wrong!

Q.11 Iterator returned by ConcurrentSkipListSet is

Fail-fast

Fail-safe

None of the above

Correct! Wrong!

Q.12 Which List is synchronized?

Vector

CopyOnWriteArrayList

Both the above

Correct! Wrong!

Q.13 Which Set is synchronized?

CopyOnWriteArraySet

ConcurrentSkipListSet

Both the above

Correct! Wrong!

Q.14 What will be the output of the following code -

a
b
a

a
b

Will print ‘a’ infinite times

a

Correct! Wrong!

Q.15 What is the significance of using instanceOf operator and getClass() in equals method?

InstanceOf can return true for comparing current class with its subclass as well

getClass() can return true only if exactly same class is compared

getClass() can return false when compared with subclass

All of the above

Correct! Wrong!

Q.16 What will be the output of the following code –

0
null

1
null

2
null

11 44

Correct! Wrong!

Q.17 What will be the output of the following code -

Compile time exception

a b c d e 1

a b c d e 2

3
null

Correct! Wrong!

See also – 
Java Quiz Part 2 & Part 3