Java Design Patterns: A Hands-On Experience with Real-World Examples

© The Author(s), under exclusive license to APress Media, LLC, part of Springer Nature 2022

V. SarcarJava Design Patternshttps://doi.org/10.1007/978-1-4842-7971-7_7

7. Singleton Pattern

Vaskaran Sarcar¹  

(1)

Garia, Kolkata, India

 

This chapter covers the Singleton pattern.

GoF Definition

It ensures that a class has only one instance and provides a global point of access to it.

Concept

Let’s assume you have a class called A and you need to create an object from it. Normally what do you do? You guess it right; you simply use the following line of code: A obA = new A();

But let’s look at it closely. If you keep using the new keyword ten more times, you’ll have ten more objects. Right? But in a real-world scenario, unnecessary object creation is a big concern ...