问答题

试题六
阅读下列说明和Java代码，将应填入(n)处的字句写在答题纸的对应栏内。
[说明]
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) soldOutStater 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) ); }
}
}