The Strategy pattern and the State pattern are both behavioral design patterns in Java, but they have different intents and implementations.
The Strategy pattern is used to encapsulate a family of algorithms and make them interchangeable. It defines a set of algorithms (or strategies) that can be selected and used at runtime based on specific requirements or conditions. The Strategy pattern involves creating a separate class for each strategy, implementing a common interface or abstract class, and allowing the client to select and use the appropriate strategy.
The State pattern, on the other hand, is used to represent the state of an object and its behavior based on that state. It allows an object to alter its behavior when its internal state changes. The State pattern involves creating a separate class for each state, implementing a common interface or abstract class, and allowing the object to change its state and behavior by delegating to the appropriate state object.
The main difference between the two patterns is that the Strategy pattern is concerned with interchangeable algorithms, while the State pattern is concerned with changing behavior based on the state of an object. In the Strategy pattern, the algorithms can be used independently of the context, while in the State pattern, the behavior is tightly coupled to the state of the object.
In summary, the Strategy pattern is used to encapsulate a family of interchangeable algorithms, while the State pattern is used to represent the state of an object and its behavior based on that state.