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

 

 

二、源码

     1、状态抽象类

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

 

     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");
	}
}

 

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

 

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

 

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

 

     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);
	}
}

 

     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
	}
}