设计模式--状态模式

 

状态模式原理

一个糖果机项目


CandyMachine

public class CandyMachine {

	final static int SoldOutState = 0;
	final static int OnReadyState = 1;
	final static int HasCoin = 2;
	final static int SoldState = 3;

	private int state = SoldOutState;
	private int count = 0;

	public CandyMachine(int count) {
		this.count = count;
		if (count > 0) {
			state = OnReadyState;
		}
	}

	public void insertCoin() {
		switch (state) {
		case SoldOutState:
			System.out.println("you can't insert coin,the machine sold out!");
			break;
		case OnReadyState:
			state = HasCoin;
			System.out.println("you have inserted a coin,next,please turn crank!");
			break;
		case HasCoin:
			System.out.println("you can't insert another coin!");

			break;
		case SoldState:
			System.out.println("please wait!we are giving you a candy!");

			break;
		}

	}

	public void returnCoin() {
		switch (state) {
		case SoldOutState:
			System.out.println("you can't return,you haven't inserted a coin yet!");
			break;
		case OnReadyState:
			System.out.println("you haven't inserted a coin yet!");
			break;
		case HasCoin:

			System.out.println("coin return!");
			state = OnReadyState;

			break;
		case SoldState:
			System.out.println("sorry,you already have turned the crank!");

			break;
		}

	}

	public void turnCrank() {
		switch (state) {
		case SoldOutState:
			System.out.println("you turned,but there are no candies!");
			break;
		case OnReadyState:
			System.out.println("you turned,but you haven't inserted a coin!");
			break;
		case HasCoin:
			System.out.println("crank turn...!");
			state = SoldState;
			dispense();
			break;
		case SoldState:
			System.out
					.println("we are giving you a candy,turning another get nothing,!");
			break;
		}

	}

	private void dispense() {
		count = count - 1;
		System.out.println("a candy rolling out!");
		if (count > 0) {
			state = OnReadyState;
		} else {
			System.out.println("Oo,out of candies");
			state = SoldOutState;
		}

	}

	public void printstate() {

		switch (state) {
		case SoldOutState:
			System.out.println("***SoldOutState***");
			break;
		case OnReadyState:
			System.out.println("***OnReadyState***");
			break;
		case HasCoin:

			System.out.println("***HasCoin***");

			break;
		case SoldState:
			System.out.println("***SoldState***");
			break;
		}

	}
}

MainTest

public class MainTest {
	public static void main(String[] args) {
		CandyMachine mCandyMachine=new CandyMachine(1);
		
		mCandyMachine.printstate();
		
		mCandyMachine.insertCoin();
		mCandyMachine.printstate();
		
		mCandyMachine.turnCrank();
		
		mCandyMachine.printstate();
		
		mCandyMachine.insertCoin();
		mCandyMachine.printstate();
		
		mCandyMachine.turnCrank();
		
		mCandyMachine.printstate();
	}
}

项目新需求的困惑


状态模式原理和解决方案

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


状态模式示例代码讲解 
示例项目类结构图


State

public interface State {
	public void insertCoin();
	public void returnCoin();
	public void turnCrank();
	public void dispense();
	public void printstate();
}

CandyMachine  

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() {

		// TODO Auto-generated method stub
		if (count > 0) {
			count = count - 1;
			System.out.println("a candy rolling out!");
		}

	}

	public int getCount() {
		return count;
	}

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

 SoldOutState 

public class SoldOutState implements State {

	private CandyMachine mCandyMachine;
	public SoldOutState(CandyMachine mCandyMachine)
	{
		this.mCandyMachine=mCandyMachine;
	}

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

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

	}

	@Override
	public void turnCrank() {
		// TODO Auto-generated method stub
		System.out.println("you turned,but there are no candies!");
		
	}

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

	}

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

}

OnReadyState 

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***");
		
	}

}

HasCoin 

import java.util.Random;

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***");

	}

}

SoldState 

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

	@Override
	public void insertCoin() {
		// TODO Auto-generated method stub
		System.out.println("please wait!we are giving you a candy!");

	}

	@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("we are giving you a candy,turning another get nothing,!");

	}

	@Override
	public void dispense() {
		// TODO Auto-generated method stub
		
		mCandyMachine.releaseCandy();
		if (mCandyMachine.getCount() > 0) {
			mCandyMachine.setState(mCandyMachine.mOnReadyState);
		} else {
			System.out.println("Oo,out of candies");
			mCandyMachine.setState(mCandyMachine.mSoldOutState);
		}

	
	
	}

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

}

WinnerState 

public class WinnerState implements State {

	private CandyMachine mCandyMachine;

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

	@Override
	public void insertCoin() {
		// TODO Auto-generated method stub
		System.out.println("please wait!we are giving you a candy!");

	}

	@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("we are giving you a candy,turning another get nothing,!");

	}

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

		
		mCandyMachine.releaseCandy();
		if (mCandyMachine.getCount() == 0) {
			mCandyMachine.setState(mCandyMachine.mSoldOutState);
		} else {
			System.out.println("you are a winner!you get another candy!");
			mCandyMachine.releaseCandy();
			if (mCandyMachine.getCount() > 0) {
				mCandyMachine.setState(mCandyMachine.mOnReadyState);
			} else {
				System.out.println("Oo,out of candies");
				mCandyMachine.setState(mCandyMachine.mSoldOutState);
			}
		}

	}

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

	}

}

MainTest 

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();
	}
}