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      在UML当中有状态机视图，这个状态机可以用于自动售货机，自动售票机等等场景，下面是用java代码模拟的一个状态机：

1.状态机接口

package stateMachine;/** * 状态机接口 * @author seacean * @date 2013-8-29 */public interface State {	/**	 * 投入硬币	 */	void insertQuarter();    /**     * 根据摇动情况，处理摇动结果，返回处理结果，释放糖果     */	void ejectQuarter();    /**     * 转动摇柄     */	void turnCrank();    /**     * 机器放出糖果，处理机器内部状态，返回初始可投币状态     */	void dispense();}

2.带有状态机的机器

package stateMachine;/** * 机器类，包含多种状态，处理流程 * @author seacean * @date 2013-8-29 */public class Machine {	//机器本身包含所有的状态机	private State soldOutState;	private State noQuarterState;	private State hasQuarterState;	private State soldState;	private State state; //机器的当前状态	private int count = 0;//机器中当前糖果的数量    /**     * 初始化机器，引入所有的状态机，初始化糖果数量，初始化机器状态     * @param count     */	public Machine(int count) {		this.soldOutState = new SoldOutState(this);		this.noQuarterState = new NoQuarterState(this);		this.hasQuarterState = new HasQuarterState(this);		this.soldState = new SoldState(this);		this.count = count;		if (this.count > 0) {			this.state = noQuarterState;		}	}    /**     * 释放糖果时的内部处理程序     */	public void releaseBall() {		System.out.println("a gumball comes rolling out the solt...");		if (count > 0) {			count -= 1;		}	}    	public void insertQuerter() {		state.insertQuarter();//加入硬币	}	public void ejectQuarter() {		state.ejectQuarter();	}	public void turnCrank() {		state.turnCrank();		state.dispense();	}	public State getSoldOutState() {		return soldOutState;	}	public State getNoQuarterState() {		return noQuarterState;	}	public State getHasQuarterState() {		return hasQuarterState;	}	public State getSoldState() {		return soldState;	}	public State getState() {		return state;	}	public int getCount() {		return count;	}	public void setState(State state) {		this.state = state;	}}

3.下面是状态机的一些实现类

package stateMachine;/** * 机器处于没有投硬币的状态 * @author seacean * @date 2013-8-29 */public class NoQuarterState implements State {	private Machine machine;	public NoQuarterState(Machine machine) {		this.machine = machine;	}	@Override	public void insertQuarter() {		System.out.println("please insert a quarter!");		machine.setState(machine.getHasQuarterState());	}	@Override	public void ejectQuarter() {		System.out.println("please insert a quarter!");	}	@Override	public void turnCrank() {		System.out.println("please insert a quarter!");	}	@Override	public void dispense() {		System.out.println("please insert a quarter!");	}}

package stateMachine;/** * 机器处于有硬币，有糖果，没有摇动的状态 * @author seacean * @date 2013-8-29 */public class HasQuarterState implements State {    private Machine machine;        public HasQuarterState(Machine machine){    	this.machine=machine;    }	@Override	public void insertQuarter() {		System.out.println("You can not insert another quarter!");	}	@Override	public void ejectQuarter() {		System.out.println("Quarter returned!");		machine.setState(machine.getNoQuarterState());	}	@Override	public void turnCrank() {		System.out.println("You turned ... ");        machine.setState(machine.getSoldState());	}	@Override	public void dispense() {		System.out.println("No gumball dispensed!");	}}

package stateMachine;/** * 机器正在出售糖果的状态 *  * @author seacean * @date 2013-8-29 */public class SoldState implements State {	private Machine machine;	public SoldState(Machine machine) {		this.machine = machine;	}	@Override	public void insertQuarter() {		System.out.println("please wait,we are already giving you a gumball!");	}	@Override	public void ejectQuarter() {		System.out.println("Sorry, you have turned the crank!");	}	@Override	public void turnCrank() {		System.out.println("Turning twice does not get you another gumball!");	}	@Override	public void dispense() {		machine.releaseBall();		if (machine.getCount() > 0) {			machine.setState(machine.getNoQuarterState());		} else {			System.out.println("Out of Gumballs!");			machine.setState(machine.getSoldOutState());		}	}}

package stateMachine;/** * 机器处于无糖果状态 * @author seacean * @date 2013-8-29 */public class SoldOutState implements State {    private Machine machine;	public SoldOutState(Machine machine) {		this.machine=machine;	}	@Override	public void insertQuarter() {		System.out.println("Sorry, there is no gumball in the machine!");	}	@Override	public void ejectQuarter() {		System.out.println("Sorry, there is no gumball in sold!");	}	@Override	public void turnCrank() {		System.out.println("Sorry, there is no gumball!Turn is no meaning.");		machine.setState(machine.getNoQuarterState());	}	@Override	public void dispense() {		System.out.println("Sorry, there is no gumball!");	}}

4.下面是测试类

package stateMachine;//测试类public class StateMachineTest {	public static void main(String[] args) {         Machine machine=new Machine(10);         for(int i=0;i<11;i++){         System.out.println(machine);         machine.insertQuerter();         machine.turnCrank();         }	}}

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