The Singleton design pattern ensures that a class has only one instance throughout the application’s lifecycle and provides a global point of access to that instance.

  • Key points:
    • Single Instance: Only one instance of the class is created.
    • Global Access: The instance can be accessed globally, ensuring shared resources.
    • Lazy Initialization: The instance is created only when it is needed, improving performance.

  • Implementation:

    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) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }
        return instance;
    }
}
  • Explanation:
    • Private Constructor: Prevents direct instantiation of the class.
    • getInstance() Method: Checks if the instance is already created, and if not, creates it. The method uses double-checked locking for thread safety.

In summary, the Singleton pattern is used to control the creation of a class instance and ensure it is used globally, making it ideal for managing shared resources like database connections or configuration settings.