试题六（共15分）

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 j ava.util.*;

interface State{

public void insertQuarter(); //投币

public void ejectQuarter(); //退币

public void turnCrank();腑安下“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(intnumbers) { /*实现代码省略 */}

public StategetHasQuarterState() { returnhasQuarterState; }

public StategetNoQuarterState() { returnnoQuarterState, }

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)); }

}

}