SingletonHolder Design Pattern in Java: Lazy Initialization & Thread Safety

SingletonHolder is a design pattern used to implement the Singleton pattern in Java. It is a nested static class that holds the instance of the Singleton class and ensures lazy initialization and thread safety. \n\nThe SingletonHolder class has a private constructor and a static final field that holds the instance of the Singleton class. The instance is created only when the getInstance() method of the SingletonHolder class is called for the first time, ensuring lazy initialization. \n\nThe SingletonHolder class also defines a static getInstance() method that returns the instance of the Singleton class. This method uses double-checked locking to ensure thread safety, preventing multiple threads from creating multiple instances of the Singleton class. \n\nOverall, the SingletonHolder pattern provides a convenient and efficient way to implement the Singleton pattern in Java, ensuring lazy initialization and thread safety without the need for explicit synchronization.