Singleton Design Pattern

Overview

The Singleton Design Pattern ensures that a class has only one instance and provides a global point of access to it. It is often used to manage shared resources like configurations, logging, or thread pools.

Key Characteristics

• Ensures only one instance of the class exists.
• Provides a global point of access to the instance.
• Controls concurrent access to the shared instance, if needed.

Implementation

The following is an example of a Singleton implementation in Java:

public class Singleton {
    private static Singleton instance;

    // Private constructor to prevent instantiation
    private Singleton() {}

    // Public method to provide access to the instance
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}
    

When to Use

• When you need exactly one instance of a class to control access to a shared resource.
• When you need global access to an instance.

Advantages

• Controlled access to the single instance.
• Reduced memory usage for shared resources.

Disadvantages

• Can introduce issues in multithreaded environments if not implemented carefully.
• Can make unit testing more challenging due to global state.

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