设计模式----状态模式

public class Context {
    //持有一个State类型的对象实例
    private State state;
    public void setState(State state) { this.state = state; }
    
    //用户感兴趣的接口方法
    public void request(String s) {
        //转调state来处理
        state.handle(s);
    }
}

public interface State {
    //状态对应的处理
    public void handle(String s);
}

//具体状态A
public class ConStateA implements State {
    public void handle(String s) {
        System.out.println("ConcreteStateA ：" + s);
    }

}
//具体状态B
public class ConStateB implements State {
    public void handle(String s) {
        System.out.println("ConcreteStateB ：" + s);
    }

}

public class Client {
    public static void main(String[] args){
        //创建状态
        State state = new ConcreteStateB();
        //创建环境
        Context context = new Context();
        //将状态设置到环境中
        context.setState(state);
        //请求
        context.request("test");
    }
}

public interface State {
	public void insertQuarter();
	public void ejectQuarter();
	public void turnCrank();
	public void dispense();
}

public class GumballMachine {
    //所有的状态都在这里
	State soldOutState;
	State noQuarterState;
	State hasQuarterState;
	State soldState;
 
	State state = soldOutState;
	int count = 0;
    //构造器取得糖果初始数目，并为每个状态创建一个状态实例
	public GumballMachine(int numberGumballs) {
		soldOutState = new SoldOutState(this);
		noQuarterState = new NoQuarterState(this);
		hasQuarterState = new HasQuarterState(this);
		soldState = new SoldState(this);
		this.count = numberGumballs;
 		if (numberGumballs > 0) {
			state = noQuarterState;
		} 
	}
 
	public void insertQuarter() {//委托当前状态
		state.insertQuarter();
	}
	public void ejectQuarter() {//委托当前状态
		state.ejectQuarter();
	}
	public void turnCrank() {//注意这里和其他两个的区别。dispense是一个内部动作，用户不能直接要求发放糖果。用户转动手柄turnCrack()方法调用dispense()
		state.turnCrank();
		state.dispense();
	}
	void setState(State state) {//允许其他对象将机器的状态转换到不同状态
		this.state = state;
	}
 
	void releaseBall() {
		System.out.println("A gumball comes rolling out the slot...");
		if (count != 0) {
			count = count - 1;
		}
	}
 
	int getCount() {
		return count;
	}
 
	void refill(int count) {
		this.count = count;
		state = noQuarterState;
	}

    public State getState() {
        return state;
    }

    public State getSoldOutState() {
        return soldOutState;
    }
    public State getNoQuarterState() {
        return noQuarterState;
    }
    public State getHasQuarterState() {
        return hasQuarterState;
    }
    public State getSoldState() {
        return soldState;
    }
 //更多方法
}

import java.util.Random;

public class HasQuarterState implements State {
	GumballMachine gumballMachine;
	public HasQuarterState(GumballMachine gumballMachine) {
		this.gumballMachine = gumballMachine;
	}
	public void insertQuarter() {
		System.out.println("You can't insert another quarter");
	}
	public void ejectQuarter() {
		System.out.println("Quarter returned");
		gumballMachine.setState(gumballMachine.getNoQuarterState());
	}
	public void turnCrank() {
		System.out.println("You turned...");
		gumballMachine.setState(gumballMachine.getSoldState());
	}
    public void dispense() {
        System.out.println("No gumball dispensed");
    }
	public String toString() {
		return "waiting for turn of crank";
	}
}

public class NoQuarterState implements State {
    GumballMachine gumballMachine;
    public NoQuarterState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }
	public void insertQuarter() {
		System.out.println("You inserted a quarter");
		gumballMachine.setState(gumballMachine.getHasQuarterState());
	}
	public void ejectQuarter() {
		System.out.println("You haven't inserted a quarter");
	}
	public void turnCrank() {
		System.out.println("You turned, but there's no quarter");
	 }
	public void dispense() {
		System.out.println("You need to pay first");
	} 
	public String toString() {
		return "waiting for quarter";
	}
}


public class SoldOutState implements State {
    GumballMachine gumballMachine;
    public SoldOutState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }
	public void insertQuarter() {
		System.out.println("You can't insert a quarter, the machine is sold out");
	}
	public void ejectQuarter() {
		System.out.println("You can't eject, you haven't inserted a quarter yet");
	}
	public void turnCrank() {
		System.out.println("You turned, but there are no gumballs");
	}
	public void dispense() {
		System.out.println("No gumball dispensed");
	}
	public String toString() {
		return "sold out";
	}
}


public class SoldState implements State {
    GumballMachine gumballMachine;
    public SoldState(GumballMachine gumballMachine) {
        this.gumballMachine = gumballMachine;
    }
	public void insertQuarter() {
		System.out.println("Please wait, we're already giving you a gumball");
	}
	public void ejectQuarter() {
		System.out.println("Sorry, you already turned the crank");
	}
	public void turnCrank() {
		System.out.println("Turning twice doesn't get you another gumball!");
	}
	public void dispense() {
		gumballMachine.releaseBall();
		if (gumballMachine.getCount() > 0) {
			gumballMachine.setState(gumballMachine.getNoQuarterState());
		} else {
			System.out.println("Oops, out of gumballs!");
			gumballMachine.setState(gumballMachine.getSoldOutState());
		}
	}
	public String toString() {
		return "dispensing a gumball";
	}
}