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144 interview questions on Javafor developers (2024)

Test your technical skills before an interview of Java with 144 corrected questions. Beginner, Intermediate or Expert level.

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144 questions
Easy
18 votes2073 runs4 comments

Write a Java program that prints 'welovedev'.

Full stack developer
strings
variables
Pierreat Sep 19, 2022
Hard
12 votes2805 runs0 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
Hard
9 votes2772 runs0 comment

A monitor in Java

Back-end developer
java
thread
Thomas De verdièreat Jan 4, 2022
Hard
8 votes2876 runs0 comment

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

Back-end developer
inheritance
package
Thomas De verdièreat Jan 4, 2022
Hard
8 votes2703 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer
array
memory
Thomas De verdièreat Dec 16, 2021
Easy
8 votes2016 runs0 comment

How should a package be named in Java?

Full stack developer
packages
java
Pierreat Sep 19, 2022
Medium
8 votes650 runs0 comment

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

Full stack developer
EL Mostafaat Feb 13, 2024
Medium
7 votes2769 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
Easy
7 votes2718 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
Easy
7 votes1965 runs1 comment

How to concatenate two strings of characters in Java?

Full stack developer
strings
concatenation
Pierreat Jan 4, 2022
Hard
6 votes2809 runs0 comment

A “synchronized” method

Back-end developer
java
method
Thomas De verdièreat Jan 4, 2022
Hard
6 votes2792 runs0 comment

Write a finalizer in Java.

Back-end developer
java
finalizer
Thomas De verdièreat Dec 16, 2021
Hard
6 votes2789 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer
serialization
interface
Thomas De verdièreat Jan 4, 2022
Hard
6 votes2742 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
Hard
5 votes2817 runs2 comments

How to write a portable Java program

Back-end developer
java
native
Thomas De verdièreat Jan 4, 2022
Hard
5 votes2773 runs0 comment

Create an instance of HashMap in Java

Back-end developer
hashmap
map
null
Thomas De verdièreat Jan 4, 2022
Hard
5 votes2704 runs0 comment

What design pattern will you use to dynamically add capabilities to an object in Java?

Back-end developer
design patterns
object
Thomas De verdièreat Jan 4, 2022
Easy
5 votes1984 runs0 comment

Are arrays primitives types in Java?

Full stack developer
arrays
primitives
Pierreat Sep 19, 2022
Easy
5 votes1949 runs0 comment

Add elements to an ArrayList in Java

Full stack developer
arrays
lists
java
Pierreat Jan 4, 2022
Hard
4 votes2812 runs0 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
Java tests