Java Singleton Pattern: Key Characteristics

Characteristics of the Java Singleton design pattern include:

1. Only one instance can exist: the singleton pattern ensures that a class has only one instance and provides a global access point.
2. Private constructor: The constructor of a singleton class must be private to prevent external classes from creating multiple instances.
3. Delay instantiation: The singleton object is only instantiated when it is first used, which can improve performance.
4. Thread safety: Singleton pattern needs to ensure thread safety in a multi-threaded environment, preventing multiple threads from creating instances at the same time.
5. Static method access unique instance: Singleton classes usually provide a static method to retrieve a reference to the unique instance.
6. Global access point: The unique instance of a singleton class can be accessed from anywhere through a global access point.
7. Singleton pattern is suitable for resource sharing scenarios, such as database connections and thread pools.