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软件设计师案例分析每日一练试题内容(2022/9/23)
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) 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) ); }
}
}
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