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79 interview questions on Javafor developers (2026)

Test your technical skills before an interview of Java with 79 corrected questions. Beginner, Intermediate or Expert level.

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79 questions
Hard
17 votes3540 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
14 votes3548 runs1 comment

Serialization can be customized with the Externalizable interface

Back-end developer
serialization
interface
Thomas De verdièreat Jan 4, 2022
Easy
14 votes3426 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
14 votes3373 runs0 comment

How many instance of Integer cannot be freed from memory?

Back-end developer
array
memory
Thomas De verdièreat Dec 16, 2021
Hard
12 votes3573 runs0 comment

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

Back-end developer
inheritance
package
Thomas De verdièreat Jan 4, 2022
Hard
12 votes3531 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
12 votes3476 runs0 comment

A monitor in Java

Back-end developer
java
thread
Thomas De verdièreat Jan 4, 2022
Hard
11 votes3423 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
Medium
10 votes3517 runs0 comment

A “synchronized” method

Back-end developer
java
method
Thomas De verdièreat Jan 4, 2022
Easy
9 votes3353 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
Medium
9 votes3315 runs2 comments

What does the following code show?

Back-end developer
java
variable
Thomas De verdièreat Jan 4, 2022
Hard
8 votes3515 runs0 comment

Write a finalizer in Java.

Back-end developer
java
finalizer
Thomas De verdièreat Dec 16, 2021
Easy
8 votes3380 runs0 comment

What is the classpath for?

Back-end developer
java
classpath
Thomas De verdièreat Jan 4, 2022
Easy
8 votes3326 runs0 comment

Java 5: where to place the "@Override" tag and why?

Back-end developer
java
annotations
Thomas De verdièreat Jan 4, 2022
Easy
7 votes3408 runs0 comment

Create an instance of ArrayList in Java

Back-end developer
array
list
Thomas De verdièreat Jan 4, 2022
Hard
7 votes3399 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
Easy
7 votes3351 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 votes3532 runs
3 comments

How to write a portable Java program

Back-end developer
java
native
Thomas De verdièreat Jan 4, 2022
Hard
6 votes3486 runs0 comment

How to create a thread in Java

Back-end developer
threads
java
Thomas De verdièreat Jan 4, 2022
Hard
6 votes3464 runs0 comment

Create an instance of HashMap in Java

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