Singleton Class in Java

Introduction#

A Singleton Class in Java is a design pattern that restricts the instantiation of a class to a single instance. It ensures that only one object of the class exists in the entire application and provides a global point of access to that instance.

Why Use Singleton Pattern?#

• To manage shared resources like database connections or configuration settings.
• To ensure controlled object creation and save memory.
• To provide global access to a single instance.

Implementing Singleton in Java (Basic Example)#

Since we have already learned about static and final, we can use them to create a Singleton class effectively.

class Singleton {
    private static final Singleton instance = new Singleton(); // Static and final instance

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

    public static Singleton getInstance() {
        return instance; // Returns the single instance
    }
}

public class Main {
    public static void main(String[] args) {
        Singleton obj1 = Singleton.getInstance();
        Singleton obj2 = Singleton.getInstance();
        System.out.println(obj1 == obj2); // Output: true (Same instance)
    }
}

Explanation:#

• static ensures that the instance is shared across the application.
• final ensures that the instance is assigned only once.
• Private Constructor prevents multiple object creation.

When to Use Singleton?#

✅ Managing configuration settings. 

✅ Handling logging frameworks. 

✅ Database connection pooling. 

❌ Not suitable for general object creation.

Conclusion#

In this blog, we learned:

• What a Singleton Class is and why it is useful.
• How static and final help in implementing Singleton.
• A simple example to illustrate Singleton.