How to avoid the copy of a Singleton class, instance using clone...

1. Make your class final (so that no cloneable sub-class can be created)
2. In case of non-final class, Override the clone method of Object
class in your class and inside the body of the method just throw a
CloneNotSupportedException.

ex:
public final class MyClass
{
protected Object clone() throws CloneNotSupportedException
{
throw new CloneNotSupportedException();
}
}