某大型商场内安装了多个简易的纸巾售卖机，自动出售2元钱一包的纸巾，且每次仅售出一包纸巾。纸巾售卖机的状态图如图6-1所示。
采用状态（State）模式来实现该纸巾售卖机，得到如图6-2所示的类图。其中类State为抽象类，定义了投币、退币、出纸巾等方法接口。类SoldState、SoldOutState、NoQuarterState和HasQuarterState分别对应图6-1中纸巾售卖机的4种状态：售出纸巾、纸巾售完、没有投币、有2元钱。
【Java代码】
import java．util.*;
interface State{
public void insertQuarter（ ）;//投币
public void ejectQuarter（ ）;//退币
public void turnCrank（ ）;//按下“出纸巾”按钮
public void dispense（ ）;//出纸巾
}
class TissueMachine{
（1）soldOutState，noQuarterState，hasQuarterState，soldState，state;
state=soldOutState;
int count=0;//纸巾数
public TissueMachine(int numbers){/*实现代码省略*/}
public State getHasQuarterState（ ）{return hasQuarterState;}
public State getNoQuarterState（ ）{return noQuarterState;}
public State getSoldState（ ）{return soldState;}
public State getSoldOutState（ ）{return soldOutState;}
public int getCount（ ）{return count;}
//其余代码省略
}
class NoQuarterState implements State{
TissueMachine tissueMachine;
public void insertQuarter（ ）{
tissueMachine.setState(（2）);
}
//构造方法以及其余代码省略
}
class HasQuarterState implements State{
TissueMachine tissueMachine;
public void ejectQuarter（ ）{
tissueMachine.setState(（3）);
}
//构造方法以及其余代码省略
}
class SoldState implements State{
TissueMachine tissueMachine;
public void dispense（ ）{
if(tissueMachine.getCount（ ）>0){
tissueMachine.setState(（4）);
}else{
tissueMachine.setState(（5）);}
}
}