設計模式： 自己手動寫一個狀態模式

 狀態模式： 允許對象在內部狀態改變時改變它的行爲，對象看起來好像修改了它的類。狀態模式將狀態封裝成獨立的類，並將動作委託到代表當前狀態的對象。狀態模式使用組合通過簡單引用不同的狀態對象來造成類改變的假象。

狀態模式和策略模式有相同的類圖，但它們的意圖不同，策略模式會用行爲和算法來配置Context類。狀態模式允許Context隨着狀態的改變而改變其行爲。

源代碼：

</pre><pre name="code" class="java">package state;
/**
 * 狀態接口
 * @author Arvon
 *
 */
public interface State {
	/**
	 * 放入25分錢
	 */
	public void insertQuarter();
	/**
	 * 取出25分錢
	 */
	public void ejectQuarter();
	/**
	 * 扭動曲軸
	 */
	public void turnCrank();
	/**
	 * 分配口香糖
	 */
	public void dispense();
	/**
	 * 重新初始化口香糖機
	 */
	public void refill();
}

package state;

import java.util.Random;

public class HasQuarterState implements State {
	Random randomWinner = new Random(System.currentTimeMillis());
	GumballMachine gumballMachine;
	public HasQuarterState(GumballMachine gumballMachine) {
		this.gumballMachine = gumballMachine;
	}

	@Override
	public void insertQuarter() {
		System.out.println("You can't insert another quarter");

	}
	
	
	@Override
	public void ejectQuarter() {
		System.out.println("Quarter returned");
		gumballMachine.setState(gumballMachine.getNoQuarterState());

	}

	@Override
	public void turnCrank() {
		System.out.println("You turned...");
		int winner = randomWinner.nextInt(10);
		boolean isWinner = (winner == 0) && (gumballMachine.getCount() > 1);
		gumballMachine.setState(isWinner?gumballMachine.getWinnerState():gumballMachine.getSoldState());
	}

	@Override
	public void dispense() {
		System.out.println("please turn the crank,or No gumball will be dispensed");
	}

	@Override
	public void refill() {
		
	}

}

package state;

public class NoQuarterState implements State {
	GumballMachine gumballMachine;
	public NoQuarterState(GumballMachine gumballMachine) {
		this.gumballMachine = gumballMachine;
	}

	@Override
	public void insertQuarter() {
		System.out.println("You inserted a quarter");
		gumballMachine.setState(gumballMachine.getHasQuarterState());

	}

	@Override
	public void ejectQuarter() {
		System.out.println("You haven't inserted a quarter");
	}

	@Override
	public void turnCrank() {
		System.out.println("You turned, but there's no quarter");
	}

	@Override
	public void dispense() {
		System.out.println("You need to pay first");
	}

	@Override
	public void refill() {
		
	}

}

package state;
/**
 * 售罄狀態
 * @author Administrator
 *
 */
public class SoldOutState implements State {
	GumballMachine mGumballMachine;
	
	public SoldOutState(GumballMachine mGumballMachine) {
		super();
		this.mGumballMachine = mGumballMachine;
	}

	@Override
	public void insertQuarter() {
		// TODO Auto-generated method stub
		System.out.println("You can't insert a quarter, the machine is sold out");

	}

	@Override
	public void ejectQuarter() {
		// TODO Auto-generated method stub
		System.out.println("You can't eject, you haven't inserted a quarter yet");
	}

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

	@Override
	public void dispense() {
		// TODO Auto-generated method stub
		System.out.println("No gumball dispensed");

	}

	@Override
	public void refill() {
		mGumballMachine.setState(mGumballMachine.getNoQuarterState());
	}

}

package state;

public class SoldState implements State {

	private GumballMachine gumballMachine;

	public SoldState(GumballMachine gumballMachine) {
		this.gumballMachine = gumballMachine;
	}

	@Override
	public void insertQuarter() {
		System.out.println("Please wait, we're already giving you a gumball");
	}

	@Override
	public void ejectQuarter() {
		System.out.println("Sorry, you already turned the crank");

	}

	@Override
	public void turnCrank() {
		System.out.println("Turning twice doesn't get you another gumball!");

	}

	@Override
	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());
		}
	}

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

}

package state;

public class WinnerState implements State {

	private GumballMachine gumballMachine;

	public WinnerState(GumballMachine gumballMachine) {
		this.gumballMachine = gumballMachine;
	}

	@Override
	public void insertQuarter() {
		System.out.println("Please wait, we're already giving you a Gumball");
	}

	@Override
	public void ejectQuarter() {
		System.out.println("Please wait, we're already giving you a Gumball");
	}

	@Override
	public void turnCrank() {
		System.out.println("Turning again doesn't get you another gumball!");
	}

	@Override
	public void dispense() {
		gumballMachine.releaseBall();
		if (gumballMachine.getCount() == 0) 
			gumballMachine.setState(gumballMachine.getSoldOutState());
		else {
			gumballMachine.releaseBall();
			System.out.println("YOU'RE A WINNER! You got two gumballs for your quarter");
			if (gumballMachine.getCount() > 0)
				gumballMachine.setState(gumballMachine.getNoQuarterState());
			else {
            	System.out.println("Oops, out of gumballs!");
				gumballMachine.setState(gumballMachine.getSoldOutState());
			}
		}
	}

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

}

package state;
/**
 * GumballMachine has soldOutState...
 * @author Administrator
 *
 */
public class GumballMachine {
	State soldOutState;
	State noQuarterState;
	State hasQuarterState;
	State soldState;
	State winnerState;
	State state = soldOutState;
	int count = 0;
	public GumballMachine(int numberGumballs) {
		soldOutState = new SoldOutState(this);
		noQuarterState = new NoQuarterState(this);
		hasQuarterState = new HasQuarterState(this);
		soldState = new SoldState(this);
		winnerState = new WinnerState(this);

		this.count = numberGumballs;
 		if (numberGumballs > 0) {
			state = noQuarterState;
		} 
	}

	public State getSoldOutState() {
		return soldOutState;
	}


	public State getSoldState() {
		return soldState;
	}


	public State getWinnerState() {
		return winnerState;
	}

	public State getNoQuarterState() {
		return noQuarterState;
	}
	public State getHasQuarterState() {
		return hasQuarterState;
	}
	
	
	public void setState(State noQuarterState) {
		state = noQuarterState;
	}
	public void insertQuarter() {
		state.insertQuarter();
	}
 
	public void ejectQuarter() {
		state.ejectQuarter();
	}
 
	public void turnCrank() {
		state.turnCrank();
		state.dispense();
	}
	public void releaseBall() {
		System.out.println("A gumball comes rolling out the slot...");
		if (count != 0) 
			count = count - 1;
	}

	public int getCount() {
		return count;
	}
	
	public String toString() {
		StringBuffer result = new StringBuffer();
		result.append("\nMighty Gumball, Inc.");
		result.append("\nJava-enabled Standing Gumball Model #2004");
		result.append("\nInventory: " + count + " gumball");
		if (count != 1) {
			result.append("s");
		}
		result.append("\n");
		result.append("Machine is " + state + "\n");
		return result.toString();
	}

}

package state;

public class StateTest {

	public static void main(String[] args) {
		GumballMachine mGumballMachine = new GumballMachine(10);
		System.out.println(mGumballMachine);
		
		mGumballMachine.ejectQuarter();
		for(int i=0;i<6;i++){
			mGumballMachine.insertQuarter();
			mGumballMachine.turnCrank();
		}
		System.out.println(mGumballMachine);
	}

}