Java

Singleton Class in Java

A Singleton class allows only one object (instance) to be created for that class throughout the entire program.

It’s useful when exactly one instance is needed to coordinate actions across the system — like Database connection, Logger, Config Manager, etc.

Code Snippet

// Singleton Class in Java
class Singleton {

    // Step 1: Create a private static instance
    private static Singleton instance;

    // Step 2: Private constructor prevents instantiation from other classes
    private Singleton() {
        System.out.println("Singleton object created");
    }

    // Step 3: Public static method to get the instance
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton(); // create only if not created already
        }
        return instance;
    }
}

public class App {
    public static void main(String[] args) {
        Singleton s1 = Singleton.getInstance();
        Singleton s2 = Singleton.getInstance();

        System.out.println(s1 == s2); // Output: true (both refer same object)
    }
}