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158 interview questions on Javafor developers (2026)

Test your technical skills before an interview of Java with 158 corrected questions. Beginner, Intermediate or Expert level.

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158 questions

Easy

38 votes3334 runs

13 comments

Write a Java program that prints 'welovedev'.

Full stack developer

strings

variables

Pierreat Sep 19, 2022

Hard

17 votes3662 runs

1 comment

How many times is the condition `(a++ < 15)` evaluated in the following code? ```java int a = 3; while (a++ < 15) { if ((a++ % 5) == 0) break; } ```

Back-end developer

loops

control flow

Thomas De verdièreat Dec 16, 2021

Easy

17 votes3226 runs

2 comments

How should a package be named in Java?

Full stack developer

packages

java

Pierreat Sep 19, 2022

Medium

15 votes1983 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

Hard

14 votes3672 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer

serialization

interface

Thomas De verdièreat Jan 4, 2022

Hard

14 votes3600 runs0 comment

A monitor in Java

Back-end developer

java

thread

Thomas De verdièreat Jan 4, 2022

Easy

14 votes3555 runs0 comment

What does the final keyword mean in front of a method in Java?

Back-end developer

java

methods

Thomas De verdièreat Jan 4, 2022

Hard

14 votes3494 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer

array

memory

Thomas De verdièreat Dec 16, 2021

Hard

13 votes3651 runs

1 comment

What is the error message when you try to serialize a class that does not implement Serializable?

Back-end developer

java

serialization

Thomas De verdièreat Dec 2, 2021

Hard

12 votes3691 runs0 comment

A Customer class has the com.company.model package.

Back-end developer

inheritance

package

Thomas De verdièreat Jan 4, 2022

Hard

11 votes3653 runs0 comment

A “synchronized” method

Back-end developer

java

method

Thomas De verdièreat Jan 4, 2022

Hard

11 votes3544 runs0 comment

What "design pattern" makes it possible to offer a means of treating the elements of a tree without worrying about the course?

Back-end developer

design pattern

tree

Thomas De verdièreat Jan 4, 2022

Easy

11 votes3069 runs

2 comments

How to concatenate two strings of characters in Java?

Full stack developer

strings

concatenation

Pierreat Jan 4, 2022

Easy

10 votes3125 runs0 comment

Add elements to an ArrayList in Java

Full stack developer

arrays

lists

java

Pierreat Jan 4, 2022

Easy

9 votes3467 runs0 comment

Which of these classes is the most suitable for composing a character string from several elements concatenated to each other?

Back-end developer

string

java

Thomas De verdièreat Jan 4, 2022

Medium

9 votes3444 runs2 comments

What does the following code show?

Back-end developer

java

variable

Thomas De verdièreat Jan 4, 2022

Easy

9 votes3150 runs0 comment

Are arrays primitives types in Java?

Full stack developer

arrays

primitives

Pierreat Sep 19, 2022

Hard

8 votes3639 runs0 comment

Write a finalizer in Java.

Back-end developer

java

finalizer

Thomas De verdièreat Dec 16, 2021

Easy

8 votes3505 runs0 comment

What is the classpath for?

Back-end developer

java

classpath

Thomas De verdièreat Jan 4, 2022

Easy

8 votes3447 runs0 comment

Java 5: where to place the "@Override" tag and why?

Back-end developer

java

annotations

Thomas De verdièreat Jan 4, 2022