Java设计模式 - 状态模式

目录

状态模式：

状态优点：

状态模式应用：

状态实例：

类图：

示例：

代码：

上述代码 GitHub 地址：https://github.com/baicun/designPatterns

状态模式：

能根据内部状态的变化，改变对象的行为，看起来好像修改了类

状态优点：

特定状态相关的行为局部化，把不同的状态隔离，耦合性低

状态模式应用：

一个对象存在多个状态（不同状态下行为不同），且状态可相互转换。

状态实例：

类图：

示例：

糖果机有如下几种状态：待机、投币、转动把手、滑落糖果、待机。不同状态绑定不同的行为，如此使用状态模式解决。

代码：

糖果机-CandyMachine.java

public class CandyMachine {

	State mSoldOutState;
	State mOnReadyState;
	State mHasCoin;
	State mSoldState;
	State mWinnerState;
	private State state;
	private int count = 0;

	public CandyMachine(int count) {
		this.count = count;
		mSoldOutState = new SoldOutState(this);
		mOnReadyState = new OnReadyState(this);
		mHasCoin = new HasCoin(this);
		mSoldState = new SoldState(this);
		mWinnerState = new WinnerState(this);
		if (count > 0) {
			state = mOnReadyState;
		} else {
			state = mSoldOutState;
		}
	}

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

	public void insertCoin() {
		state.insertCoin();
	}

	public void returnCoin() {
		state.returnCoin();
	}

	public void turnCrank() {
		state.turnCrank();
		state.dispense();
	}

	void releaseCandy() {

		if (count > 0) {
			count = count - 1;
			System.out.println("a candy rolling out!");
		}

	}

	public int getCount() {
		return count;
	}

	public void printstate() {
		state.printstate();
	}
}

状态接口-State.java

public interface State {
	//塞入硬币
	public void insertCoin();
	//返回硬币
	public void returnCoin();
	//转动把手
	public void turnCrank();
	//分发
	public void dispense();
	//当前状态
	public void printstate();
}

待机状态-OnReadyState.java

public class OnReadyState implements State {
	private CandyMachine mCandyMachine;
	public OnReadyState(CandyMachine mCandyMachine)
	{
		this.mCandyMachine=mCandyMachine;
	}

	@Override
	public void insertCoin() {
		// TODO Auto-generated method stub
		System.out.println("you have inserted a coin,next,please turn crank!");
		mCandyMachine.setState(mCandyMachine.mHasCoin);
	}

	@Override
	public void returnCoin() {
		// TODO Auto-generated method stub
		System.out.println("you haven't inserted a coin yet!");
		
	}

	@Override
	public void turnCrank() {
		// TODO Auto-generated method stub
		System.out.println("you turned,but you haven't inserted a coin!");
		
	}

	@Override
	public void dispense() {
		// TODO Auto-generated method stub

	}

	@Override
	public void printstate() {
		// TODO Auto-generated method stub
		System.out.println("***OnReadyState***");
		
	}

}

塞入硬币-HasCoin.java

public class HasCoin implements State {
	private CandyMachine mCandyMachine;

	public HasCoin(CandyMachine mCandyMachine) {
		this.mCandyMachine = mCandyMachine;
	}

	@Override
	public void insertCoin() {
		// TODO Auto-generated method stub
		System.out.println("you can't insert another coin!");

	}

	@Override
	public void returnCoin() {
		// TODO Auto-generated method stub
		System.out.println("coin return!");
		mCandyMachine.setState(mCandyMachine.mOnReadyState);
	}

	@Override
	public void turnCrank() {
		// TODO Auto-generated method stub
		System.out.println("crank turn...!");
		Random ranwinner=new Random();
		int winner=ranwinner.nextInt(10);
		if(winner==0)
		{
			mCandyMachine.setState(mCandyMachine.mWinnerState);

		}else
		{
			mCandyMachine.setState(mCandyMachine.mSoldState);

		}
		
	}

	@Override
	public void dispense() {
	}

	@Override
	public void printstate() {
		// TODO Auto-generated method stub
		System.out.println("***HasCoin***");

	}

}

测试类：

public class MainTest {
	public static void main(String[] args) {
		CandyMachine mCandyMachine = new CandyMachine(6);

		mCandyMachine.printstate();

		mCandyMachine.insertCoin();
		mCandyMachine.printstate();

		mCandyMachine.turnCrank();

		mCandyMachine.printstate();

		mCandyMachine.insertCoin();
		mCandyMachine.printstate();

		mCandyMachine.turnCrank();

		mCandyMachine.printstate();
	}
}

上述代码 GitHub 地址：https://github.com/baicun/designPatterns