软件设计-状态模式

public class 状态模式 {
    public static void main(String[] args)
    {
        Context context=new Context();
        context.Request();
        context.Request();
        context.Request();
        //System.out.println(context.getState());
        context.Request();
        context.Request();
    }
}
class Context{
    private int index;
    private State state;
    public Context()
    {
        index=3;
        state=new StateA();
    }
    public void setIndex(int index)
    {
        this.index=index;
    }
    public void setState(State state)
    {
        this.state=state;
    }
    public int getIndex()
    {
        return index;
    }
    public State getState()
    {
        return state;
    }
    public void Request()
    {
        state.Handle(this);
    }
}
interface State{
    public void Handle(Context context);
}
class StateA implements State{
    @Override
    public void Handle(Context context)
    {
        int index=context.getIndex();
        if(index>=1)
        {
            System.out.println("购买成功");
            index=index-1;
            context.setIndex(index);
            if(index==0)
            {
                context.setState(new StateB());
            }
        }else
            System.out.println("购买失败");
    }

}
class StateB implements State{
    @Override
    public void Handle(Context context)
    {
        int index=context.getIndex();
        if(index==0)
        {
            System.out.println("购买失败，需要补货");

            index=index+5;
            System.out.println("补货成功,请重新购买");
            context.setIndex(index);
            context.setState(new StateA());
        }
    }

}

运行结果