Singleton class in Java and how can we make a class as singleton?

Singleton class is a class whose only one instance can be created at any given time in one JVM.

• Make constructor as private, so that instance cannot be created outside the class.
• Private static instance needs to be created in that class itself.
• Static method should created a new instance if the value is null. Otherwise it should return the old instance. New instance creation will be avoided.