The prototype pattern is used in cases where the cost of creating a new object is much more than simply editing the attributes of an already existing object. So this pattern should be used when one has the privileges to modify the desired attributes of the object.
In java, the prototype of an object can be got by using the clone method. The method...

The Singleton pattern is used for classes which should have only one instance in the application. The other classes can't invoke the constructor directly because it is declared private and some public static method is provided which returns the single instance. This pattern makes the instance available globaly and thus should be used...

The Abstract factory pattern goes one level above in abstraction than Factory pattern. Here a concrete factory is provided for each concrete class and these concrete factories implement an abstract factory class. The advantage is that a single reference to abstract factory can be used to reference the concrete factories. This way all concrete...