状态模式

状态模式：允许对象在内部状态改变时改变它的行为，对象看起来好像修改了它的类。以下是例子：

public interface Weather {  

String getWeather(); }

 

public class Rain implements Weather {  

public String getWeather() { return "下雨"; } }

 

public class Sunshine implements Weather {  

public String getWeather() { return "阳光"; } }

 

public class Context {  

private Weather weather;

public void setWeather(Weather weather){

this.weather = weather; }

public Weather getWeather(){

return weather; }

public String weatherMessage(){

return weather.getWeather(); } }

 

//测试类

public class Test {  

public static void main(String[] args) {

Context ctx1 = new Context();

ctx1.setWeather(new Sunshine());

System.out.println(ctx1.weatherMessage());

System.out.println("==============");

Context ctx2 = new Context();

ctx2.setWeather(new Rain());

System.out.println(ctx2.weatherMessage()); } }