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55 interview questions on Java - Fundamentalsfor developers (2026)

Test your technical skills before an interview of Java - Fundamentals with 55 corrected questions. Beginner, Intermediate or Expert level.

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55 questions
Easy
38 votes3292 runs
13 comments

Write a Java program that prints 'welovedev'.

Full stack developer
strings
variables
Pierreat Sep 19, 2022
Easy
17 votes3187 runs
2 comments

How should a package be named in Java?

Full stack developer
packages
java
Pierreat Sep 19, 2022
Medium
15 votes1937 runs
1 comment

What is the difference between an interface and an abstract class in Java?

Full stack developer
EL Mostafa Fadiliat Feb 13, 2024
Easy
11 votes3033 runs
2 comments

How to concatenate two strings of characters in Java?

Full stack developer
strings
concatenation
Pierreat Jan 4, 2022
Easy
10 votes3089 runs0 comment

Add elements to an ArrayList in Java

Full stack developer
arrays
lists
java
Pierreat Jan 4, 2022
Easy
9 votes3110 runs0 comment

Are arrays primitives types in Java?

Full stack developer
arrays
primitives
Pierreat Sep 19, 2022
Easy
7 votes2894 runs0 comment

What does `--` do in Java?

Full stack developer
operators
Pierreat Jan 4, 2022
Easy
7 votes2673 runs
3 comments

How to print an array in Java

Full stack developer
arrays
java
Pierreat Feb 6, 2024
Medium
7 votes2489 runs
9 comments

What are the modifiers that cannot be used with enums in Java?

Full stack developer
enums
Xiaoyuat May 12, 2023
Easy
7 votes1462 runs
3 comments

Compare two strings in Java

Full stack developer
EL Mostafa Fadiliat Apr 8, 2024
Easy
6 votes2944 runs
3 comments

Write a valid code comment in Java

Full stack developer
comments
java
Pierreat Jan 4, 2022
Easy
6 votes1961 runs
1 comment

Given the following code, what will be displayed in the console?

Full stack developer
operators
modulo
Abderrazzak ATIFIat Nov 3, 2023
Easy
6 votes928 runs
3 comments

What is the benefit of using a ReentrantLock in Java?

Full stack developer
synchronisation
verrouillage
Anonymous authorat Dec 26, 2024
Easy
5 votes2991 runs
3 comments

What is “AssertEquals” used for in a Java Unit test?

Full stack developer
java
unit test
Pierreat Jan 4, 2022
Easy
5 votes1737 runs
1 comment

Print the result of the division of 5 by 2 in Java

Full stack developer
EL Mostafa Fadiliat Jan 25, 2024
Easy
5 votes1591 runs0 comment

What Java keyword is used to define a constant variable?

Full stack developer
EL Mostafa Fadiliat Mar 27, 2024
Hard
4 votes3144 runs5 comments

List the annotations that can be used in a JUnit test class.

Full stack developer
junit
annotations
Pierreat Jan 4, 2022
Easy
4 votes2661 runs
2 comments

How to call an interface in a java class?

Full stack developer
interfaces
java
Pierreat Jan 4, 2022
Easy
4 votes457 runs
1 comment

These two interfaces belong to the same package. Does the code compile? @FunctionalInterface public interface SimpleInterface { int compute(int a, int b); } @FunctionalInterface public interface SuperSimpleInterface extends SimpleInterface { int sum(int a, int b); }

Full stack developer
koceila MELLLAZat Jul 21, 2025
Medium
4 votes420 runs0 comment

Count the number of words in a string in Java

Full stack developer
hashmap
string
Pierreat Jan 4, 2022