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54 interview questions on Java - Fundamentalsfor developers (2026)

Test your technical skills before an interview of Java - Fundamentals with 54 corrected questions. Beginner, Intermediate or Expert level.

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54 questions
Easy
40 votes3359 runs
13 comments

Write a Java program that prints 'welovedev'.

Full stack developer
strings
variables
Pierreat Sep 19, 2022
Easy
17 votes3249 runs
2 comments

How should a package be named in Java?

Full stack developer
packages
java
Pierreat Sep 19, 2022
Medium
15 votes2006 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 votes3147 runs0 comment

Add elements to an ArrayList in Java

Full stack developer
arrays
lists
java
Pierreat Jan 4, 2022
Easy
11 votes3091 runs
2 comments

How to concatenate two strings of characters in Java?

Full stack developer
strings
concatenation
Pierreat Jan 4, 2022
Easy
9 votes3172 runs0 comment

Are arrays primitives types in Java?

Full stack developer
arrays
primitives
Pierreat Sep 19, 2022
Easy
7 votes2951 runs0 comment

What does `--` do in Java?

Full stack developer
operators
Pierreat Jan 4, 2022
Easy
7 votes2696 runs
3 comments

How to print an array in Java

Full stack developer
arrays
java
Pierreat Feb 6, 2024
Medium
7 votes2558 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 votes1520 runs
3 comments

Compare two strings in Java

Full stack developer
EL Mostafa Fadiliat Apr 8, 2024
Easy
6 votes3002 runs
3 comments

Write a valid code comment in Java

Full stack developer
comments
java
Pierreat Jan 4, 2022
Easy
6 votes2024 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 votes1654 runs0 comment

What Java keyword is used to define a constant variable?

Full stack developer
EL Mostafa Fadiliat Mar 27, 2024
Medium
6 votes993 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 votes3052 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 votes1796 runs
1 comment

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

Full stack developer
EL Mostafa Fadiliat Jan 25, 2024
Hard
4 votes3190 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 votes2680 runs
2 comments

How to call an interface in a java class?

Full stack developer
interfaces
java
Pierreat Jan 4, 2022
Easy
4 votes519 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 votes425 runs0 comment

Count the number of words in a string in Java

Full stack developer
hashmap
string
Pierreat Jan 4, 2022