Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
Participants
- Context: defines the interface of interest to clients Maintains an instance of a ConcreteState subclass that defines the current state.
- State: defines an interface for encapsulating the behavior associated with a particular state of the Context.
- Concrete State: each subclass implements a behavior associated with a state of Context
Code
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | public class Main { public static void main(String[] args) { Context c = new Context(new ConcreteStateA()); c.request(); c.request(); c.request(); c.request(); }}public interface State { void handle(Context context);}public class ConcreteStateA implements State { @Override public void handle(Context context) { context.setState(new ConcreteStateB()); }}public class ConcreteStateB implements State { @Override public void handle(Context context) { context.setState(new ConcreteStateA()); }}public class Context { private State state; public Context(State state) { setState(state); } public State getState() { return state; } public void setState(State state) { this.state = state; System.out.println("State: " + state.getClass().getSimpleName()); } public void request() { state.handle(this); }} |
Output
1 2 3 4 5 | State: ConcreteStateAState: ConcreteStateBState: ConcreteStateAState: ConcreteStateBState: ConcreteStateA |
eidherjulian61 / design-patterns
| Published on Java Code Geeks with permission by Eidher Julian, partner at our JCG program. See the original article here: State Pattern Opinions expressed by Java Code Geeks contributors are their own. |
