状态模式（State Pattern）

一、状态模式需要两种类型实体参与：

???? 1、状态管理器

?????2、状态抽象类或接口

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二、源码

???? 1、状态抽象类

public abstract class State {public abstract void turn(Context context);}

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???? 2、状态子类

public class East extends State {public void turn(Context context){context.setState(new South());System.out.println("方向转变：东到南");}}

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public class South extends State {public void turn(Context context){context.setState(new West());System.out.println("方向转变：南到西");}}

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public class West extends State {public void turn(Context context){context.setState(new North());System.out.println("方向转变：西到北");}}

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public class North extends State {public void turn(Context context){context.setState(new East());System.out.println("方向转变：北到东");}}

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???? 3、状态管理器

public class Context {private State state;public State getState() {return state;}public void setState(State state) {this.state = state;}public Context(){this.state = new East();}public void turn(){this.state.turn(this);}}

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???? 4、测试类

public class Test {public static void main(String[] args) {Context c = new Context();c.turn(); //东到南c.turn(); //南到西c.turn(); //西到北c.turn(); //北到东}}

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