Design Patterns Explained: A New Perspective on Object-Oriented Design, Second Edition

Chapter 21. The Singleton Pattern and the Double-Checked Locking Pattern

Overview

In this chapter

This chapter continues the e-commerce case study introduced in Chapter 9, “The Strategy Pattern.”

This chapter

•   Illustrates how a factory can control the number of instances of an object that can ever exist, using the Singleton pattern.

•   Describes the key features of the Singleton pattern.

•   Introduces a variant to the Singleton called the Double-Checked Locking pattern.

•   Describes some of my experiences using the Singleton pattern in practice.

The Singleton pattern and the Double-Checked Locking pattern are very simple and very common. Both are used to ensure that only one object of a particular class is instantiated. The distinction ...