java学习笔记-设计模式21(状态模式)

意图

　　允许一个对象在其内部状态改变时改变它的行为。对象看起来似乎修改了它的类。

public class State {  

    private String value;  

    public String getValue() {
        return value;
    }  

    public void setValue(String value) {
        this.value = value;
    }  

    public void method1(){
        System.out.println("execute the first opt!");
    }  

    public void method2(){
        System.out.println("execute the second opt!");
    }
}

public class Context {  

    private State state;  

    public Context(State state) {
        this.state = state;
    }  

    public State getState() {
        return state;
    }  

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

    public void method() {
        if (state.getValue().equals("state1")) {
            state.method1();
        } else if (state.getValue().equals("state2")) {
            state.method2();
        }
    }
}

public class Test {  

    public static void main(String[] args) {  

        State state = new State();
        Context context = new Context(state);  

        //设置第一种状态
        state.setValue("state1");
        context.method();  

        //设置第二种状态
        state.setValue("state2");
        context.method();
    }
}

　　转自：http://blog.csdn.net/zhangerqing/article/details/8245537