77 interview questions on Java for developers (2025)

Hard

15 votes3101 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

11 votes3055 runs0 comment

A monitor in Java

Back-end developer

java

thread

Thomas De verdièreat Jan 4, 2022

Hard

10 votes3092 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer

serialization

interface

Thomas De verdièreat Jan 4, 2022

Easy

10 votes3038 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

10 votes2968 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer

array

memory

Thomas De verdièreat Dec 16, 2021

Hard

9 votes3158 runs0 comment

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

Back-end developer

inheritance

package

Thomas De verdièreat Jan 4, 2022

Hard

9 votes3022 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

9 votes2978 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

8 votes3004 runs0 comment

What is the classpath for?

Back-end developer

java

classpath

Thomas De verdièreat Jan 4, 2022

Hard

7 votes3097 runs0 comment

A “synchronized” method

Back-end developer

java

method

Thomas De verdièreat Jan 4, 2022

Hard

7 votes3096 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

Hard

7 votes3073 runs0 comment

Write a finalizer in Java.

Back-end developer

java

finalizer

Thomas De verdièreat Dec 16, 2021

Hard

7 votes2992 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 votes2973 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

6 votes3034 runs

2 comments

What package contains the HashMap class in Java?

Back-end developer

java

hashmap

Thomas De verdièreat Jan 4, 2022

Hard

6 votes3024 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

Easy

6 votes2867 runs0 comment

Declare a constant in Java

Back-end developer

constants

java

Thomas De verdièreat Jan 4, 2022

Hard

5 votes3094 runs

3 comments

How to write a portable Java program

Back-end developer

java

native

Thomas De verdièreat Jan 4, 2022

Hard

5 votes3040 runs0 comment

Create an instance of HashMap in Java

Back-end developer

hashmap

map

null

Thomas De verdièreat Jan 4, 2022

Medium

5 votes3039 runs0 comment

Which executable is used to obtain a thread dump?

Back-end developer

java

jstack

Thomas De verdièreat Jan 4, 2022

77 interview questions on Javafor developers (2025)

Test your technical skills before an interview of Java with 77 corrected questions. Beginner, Intermediate or Expert level.

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; } ```

A monitor in Java

Serialization can be customized with the Externalizable interface

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

How many instance of Integer cannot be freed from memory?

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

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

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

What is the classpath for?

A “synchronized” method

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

Write a finalizer in Java.

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

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

What package contains the HashMap class in Java?

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

Declare a constant in Java

How to write a portable Java program

Create an instance of HashMap in Java

Which executable is used to obtain a thread dump?