Singleton design pattern

The Singleton pattern is a creational design pattern, it is one of the simplest design patterns in Java. According to the singleton design pattern, the class provides the same single object for each call--that is, it is restricting the instantiation of a class to one object and provides a global point of access to that class. So the class is responsible for creating an object and also ensures that only a single object should be created for each client call for this object. This class doesn't allow a direct instantiation of an object of this class. It allows you to get an object instance only by an exposed static method.

This is useful when exactly one object is needed to coordinate actions across the system. You can create a single pattern using two forms, as listed here:

• Early instantiation: Creation of instance at load time
• Lazy instantiation: Creation of instance when required

Benefits of the Singleton pattern:

• It provides controller access to crucial (usually heavy object) classes, such as the connection class for DB and the SessionFactory class in hibernate
• It saves heaps of memory
• It is a very efficient design for multithreaded environments
• It is more flexible because the class controls the instantiation process, and the class has the flexibility to change the instantiation process
• It has low latency