Singleton

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

Structure

• Private constructor: This prevents other classes from creating new instances.
• Static private instance: This holds the single instance of the class.
• Static method (getInstance): Provides a global point of access to the instance.

Example

class Singleton {
    // Step 1: Create a private static instance of the class.
    private static Singleton instance;

    // Step 2: Make the constructor private to prevent instantiation.
    private Singleton(){
        System.out.println("Object Created");
        ...
    }

    // Step 3: Provide a public static method to get the instance.
    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

public class Main{
    public static void main(String[] args){
        Singleton a1 = Singleton.getInstance();
        Singleton a2 = Singleton.getInstance();
        Singleton a3 = Singleton.getInstance();
        Singleton a4 = Singleton.getInstance();
        Singleton a5 = Singleton.getInstance();
        // Singleton a2 = new Singleton();
    }
}