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78 interview questions on Javafor developers (2025)

Test your technical skills before an interview of Java with 78 corrected questions. Beginner, Intermediate or Expert level.

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78 questions
Hard
16 votes3223 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
12 votes3214 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer
serialization
interface
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3173 runs0 comment

A monitor in Java

Back-end developer
java
thread
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3073 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer
array
memory
Thomas De verdièreat Dec 16, 2021
Easy
11 votes3133 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 votes3130 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
10 votes3274 runs0 comment

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

Back-end developer
inheritance
package
Thomas De verdièreat Jan 4, 2022
Hard
9 votes3219 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
Easy
9 votes3066 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 votes3211 runs0 comment

A “synchronized” method

Back-end developer
java
method
Thomas De verdièreat Jan 4, 2022
Easy
8 votes3100 runs0 comment

What is the classpath for?

Back-end developer
java
classpath
Thomas De verdièreat Jan 4, 2022
Hard
7 votes3198 runs0 comment

Write a finalizer in Java.

Back-end developer
java
finalizer
Thomas De verdièreat Dec 16, 2021
Hard
7 votes3095 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 votes3074 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
6 votes3136 runs0 comment

How to create a class in Java with a version number of 14.

Back-end developer
java
class
Thomas De verdièreat Dec 3, 2021
Medium
6 votes3133 runs
2 comments

What package contains the HashMap class in Java?

Back-end developer
java
hashmap
Thomas De verdièreat Jan 4, 2022
Easy
6 votes3099 runs1 comment

What are the visibility modifiers for a method in Java?

Back-end developer
access modifiers
methods
Thomas De verdièreat Jan 4, 2022
Easy
6 votes2959 runs0 comment

Declare a constant in Java

Back-end developer
constants
java
Thomas De verdièreat Jan 4, 2022
Hard
5 votes3207 runs
3 comments

How to write a portable Java program

Back-end developer
java
native
Thomas De verdièreat Jan 4, 2022
Hard
5 votes3161 runs0 comment

Create an instance of HashMap in Java

Back-end developer
hashmap
map
null
Thomas De verdièreat Jan 4, 2022