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157 interview questions on Javafor developers (2025)

Test your technical skills before an interview of Java with 157 corrected questions. Beginner, Intermediate or Expert level.

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157 questions
Easy
32 votes2916 runs
12 comments

Write a Java program that prints 'welovedev'.

Full stack developer
strings
variables
Pierreat Sep 19, 2022
Hard
16 votes3394 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
Hard
13 votes3240 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer
array
memory
Thomas De verdièreat Dec 16, 2021
Easy
13 votes2826 runs
2 comments

How should a package be named in Java?

Full stack developer
packages
java
Pierreat Sep 19, 2022
Medium
13 votes1528 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
12 votes3442 runs0 comment

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

Back-end developer
inheritance
package
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3405 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer
serialization
interface
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3340 runs0 comment

A monitor in Java

Back-end developer
java
thread
Thomas De verdièreat Jan 4, 2022
Easy
12 votes3290 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
11 votes3412 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
11 votes3295 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 votes2706 runs
2 comments

How to concatenate two strings of characters in Java?

Full stack developer
strings
concatenation
Pierreat Jan 4, 2022
Easy
9 votes3220 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
Hard
8 votes3378 runs0 comment

A “synchronized” method

Back-end developer
java
method
Thomas De verdièreat Jan 4, 2022
Easy
8 votes3252 runs0 comment

What is the classpath for?

Back-end developer
java
classpath
Thomas De verdièreat Jan 4, 2022
Easy
8 votes2737 runs0 comment

Add elements to an ArrayList in Java

Full stack developer
arrays
lists
java
Pierreat Jan 4, 2022
Hard
7 votes3379 runs0 comment

Write a finalizer in Java.

Back-end developer
java
finalizer
Thomas De verdièreat Dec 16, 2021
Hard
7 votes3265 runs1 comment

What is the superclass of Integer, Long, Byte, BigDecimal and Short in Java?

Back-end developer
java
superclass
Thomas De verdièreat Jan 4, 2022
Medium
7 votes3218 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
Hard
7 votes3189 runs2 comments

What does the following code show?

Back-end developer
java
variable
Thomas De verdièreat Jan 4, 2022
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