设计模式之状态模式

public class Work {
private State current;
private double hour;
private boolean finish = false;

public boolean isFinish() {
    return finish;
}
public void setFinish(boolean finish) {
    this.finish = finish;
}
public double getHour() {
    return hour;
}
public void setHour(double hour) {
    this.hour = hour;
}
public Work() {
    current = new ForenoonState();
}
public void SetState(State s) {
    current = s;
}
public void WriteProgram() {
    current.WriteProgram(this);
}
}
public abstract class State {
public abstract void WriteProgram(Work w);
}
public class ForenoonState extends State {
public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    if(w.getHour() < 12) {
        System.out.println("当前时间" + w.getHour() + "点，上午工作，精神百倍");
    } else {
        //大于12点，转入中午的状态
        w.SetState(new NoonState());
        w.WriteProgram();
    }
}
}
public class NoonState extends State {
public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    if(w.getHour() < 13) {
        System.out.println("当前时间" + w.getHour() + "点，午休");
    } else {
        //大于13点了，转入下午的工作状态
        w.SetState(new AfternoonState());
        w.WriteProgram();
    }
}
}
public class AfternoonState extends State {

public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    if(w.getHour() < 17) {
        System.out.println("当前时间" + w.getHour() + "点，下午状态不错，继续努力");
    } else {
        //大于17点了，转入晚上的加班状态
        w.SetState(new EveningState());
        w.WriteProgram();
    }
}
}
public class ResetState extends State {
public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    System.out.println("当前时间：" + w.getHour() + "已完成工作可以下班回家了");
}
}
public class EveningState extends State {

public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    if(w.isFinish()) {
        //任务完成，转入下班的状态
        w.SetState(new ResetState());
        w.WriteProgram();
    } else {
        if(w.getHour() < 21) {
            System.out.println("当前时间" + w.getHour() + "点，加班状态，疲惫至极");
        } else {
            //已经超过21点，转入睡眠状态了
            w.SetState(new SleepingState());
            w.WriteProgram();
        }
    }
}
}
public class SleepingState extends State {
public void WriteProgram(Work w) {
    // TODO Auto-generated method stub
    System.out.println("当前时间：" + w.getHour() + "点，加班睡着了");
}
}
public class Test {
public static void main(String[] args) {
    // TODO Auto-generated method stub
    Work w = new Work();
    w.setHour(9);
    w.WriteProgram();

    w.setHour(10);
    w.WriteProgram();

    w.setHour(12);
    w.WriteProgram();

    w.setHour(13);
    w.WriteProgram();

    w.setHour(14);
    w.WriteProgram();

    w.setHour(17);
    w.WriteProgram();

    w.setFinish(false);
    w.WriteProgram();

    w.setHour(19);
    w.WriteProgram();

    w.setHour(22);
    w.WriteProgram();
}
}

状态模式：当一个对象的内在状态改变时允许改变其行为，这个对象看起来像是改变了其类。

好处：
将与特定状态相关的行为局部化，且将不同状态的行为分割开来，将特定状态相关的行为都放入一个对象中，由于所有与状态相关的代码都存在于某个ConcreteState中，所以通过定义新的子类可以很容易的增加新的状态和转换。

用处：
当一个对象的行为取决于他的状态，并且必须在运行时刻根据状态改变它的行为时应考虑使用状态模式。