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();

}

}

}