StateTest.java

package JavaPatternDemos;

/**
 * State
 * 状态的具体动作被隐藏，
 * 状态的改变通常是非人为的
 *
 * 下面实现红蓝两种状态相互转化,可以更加复杂，感觉还是很实用的,
 *
 * 特别对于状态优先，状态之间转化关系明确的情况
 */

public class StateTest {
 public static void main(String[] args) {
 Context cont = new Context(new StateBlue());
 for (int i = 0; i <5 ; i++) {
 cont.operate();
 }
 }
}


class Context {

 private State state = null;
 public Context(State init_state){
 state = init_state;
 }

 public void operate(){
 state.handler_state(this);
 }

 public void setState(State newState){
 this.state = newState;
 }

}


abstract class State{
 public abstract void handler_state(Context cont);
}

class StateBlue extends State{

 @Override
 public void handler_state(Context cont) {
 // od something and change
 System.out.println("this is state blue");
 State nextState = new StateRed();
 cont.setState(nextState);
 }
}

class StateRed extends State{
 @Override
 public void handler_state(Context cont) {
 System.out.println("this is stae red");
 // do somthing
 State nexState = new StateBlue();
 cont.setState(nexState);
 }
}