State pattern is used to change the behavior of an object when the state is changed. With the change in state, the behavior of that object is completely changed. This article demonstrates State pattern implementations in Java.
Observer pattern is used to automatically notify state change in object to all its dependent objects. It works as a pub/sub for state change between objects. This article demonstrates Observer pattern implementations in Java.
Memento pattern is used to store the history of state changes of an object so that that history can be used to track back the change or be used for some other purpose. This article demonstrates Memento pattern implementations in Java.
Mediator pattern is used to restrict direct interaction between objects. A mediator class works as the middleman/communicator when one object wants to connect/use another object. This article demonstrates Mediator pattern implementations in Java.