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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
31 votes2898 runs
12 comments

Write a Java program that prints 'welovedev'.

Full stack developer
strings
variables
Pierreat Sep 19, 2022
Hard
16 votes3374 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 votes3224 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 votes2809 runs
2 comments

How should a package be named in Java?

Full stack developer
packages
java
Pierreat Sep 19, 2022
Medium
13 votes1511 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 votes3388 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer
serialization
interface
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3326 runs0 comment

A monitor in Java

Back-end developer
java
thread
Thomas De verdièreat Jan 4, 2022
Easy
12 votes3273 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 votes3426 runs0 comment

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

Back-end developer
inheritance
package
Thomas De verdièreat Jan 4, 2022
Hard
11 votes3392 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 votes3280 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 votes2690 runs
2 comments

How to concatenate two strings of characters in Java?

Full stack developer
strings
concatenation
Pierreat Jan 4, 2022
Easy
9 votes3205 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 votes3356 runs0 comment

A “synchronized” method

Back-end developer
java
method
Thomas De verdièreat Jan 4, 2022
Easy
8 votes3233 runs0 comment

What is the classpath for?

Back-end developer
java
classpath
Thomas De verdièreat Jan 4, 2022
Easy
8 votes2723 runs0 comment

Add elements to an ArrayList in Java

Full stack developer
arrays
lists
java
Pierreat Jan 4, 2022
Hard
7 votes3359 runs0 comment

Write a finalizer in Java.

Back-end developer
java
finalizer
Thomas De verdièreat Dec 16, 2021
Hard
7 votes3246 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 votes3201 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
Medium
7 votes3173 runs2 comments

What does the following code show?

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