Java语言程序设计(基础篇)原书第十一版 梁勇 第9章 课后题答案

9.1设计一个名为Rectangle的类表示矩形publicclassTest{publicstaticvoidmain(String[]args){Rectanglerectanglel=newRectangle(4,40);System.out.println("矩形的宽是"+rectanglel.width+",高是"+rectanglel.height+"z面积是"+rectanglel・getArea()+”，周长是n+rectanglel.getPerimeter());Rectanglerectangle2=newRectangle(3.5,35.9);System.out.print("矩形的宽是"+rectangle2.width+",高是"+rectangle2.height+",面积是,,+rectangle2.getArea()+,1,周长是,,+rectangle2.getPerimeter());}}classRectangle{doublewidth=l;doubleheight=l;Rectangle(){}RectanglefdoublenewWidth,doublenewHeight){width=newWidth;height=newHeight;}doublegetArea(){returnwidth*height;}doublegetPerimeter(){return(width+height)*2;〃C:\ProgramFiles\java\jdkl.8.0_101\bin\java.exe〃...矩形的宽是4.0,髙是40.0,面积是160.0,周长是88.0矩形的宽是3・5,高是35.9,面积是125.64999999999999,周长是78・8Processfinishedwithexitcode09.3使用Date类publicclassTest{publicstaticvoidmain(String[]args){Datedate=newDate();long1=10000;for(inti=1;i<9;i++){date.setTime(l);printDate(l,date);l*=10;}}publicstaticvoidprintDateflongI,Datedate){System.out.println(l+n:n+date.toString());C:\ProgramFiles'java'jdkl.8・0_101\bin\ja10000:ThuJan0108:00:10CST1970100000:ThuJan0108:01:40CST19701000000:ThuJan0108:16:40CST197010000000:ThuJan0110:46:40CST1970100000000:FriJan0211:46:40CST19701000000000:MonJan1221:46:40CST197010000000000:MonApr2701:46:40CST1970100000000000:SatMar0317:46:40CST1973Processfinishedwithexitcode09.4使用Random类publicclassTest{publicstaticvoidmain(String[]args){Randomrandom=newRandom(lOOO);for(inti=l;i<51;i++){System.out.print(random・nextlnt(100)+”\t“);if(i%10==0){System.out.printlnf);}}}}“C:\ProgrQmFiles\java\jdkl.8.0_101\bi87357624924941456450795972833675462234122718929342494235763205295873199187929155584719558877738Processfinishedwithexitcode09.6秒表publicclassTest{publicstaticvoidmain(String[]args){StopWatchstopWatch=newStopWatch();stopWatch.start();int[]a=newint[100000];for(inti=0;i<100000;i++){a[i]=(int)(Math.random()*200);}count(a);stopWatch.stop();System.out.printf"测试所用时间为:"+stopWatch.getElapsedTime()+"ms");}publicstaticvoidcount(int[]a){intmax;inttmp;for(inti=0;i<a」ength;i++){max=i;forfintj=i+l;j<a」ength;j++){if(a[max]<a[jj)max=j;}if(i!=max){tmp=a[i];a[i]=a[max];a[max]=tmp;}}}}classStopWatch{privatelongstartTime;privatelongendTime;StopWatch(){startTime=System.currentTimeMillis();}publicvoidstart(){startTime=System.currentTimeMillis();}"C:\ProgramFiles\java\jdk1・"C:\ProgramFiles\java\jdk1・8・0测试所用时间为;12406msProcessfinishedwithexitcode}publiclonggetElapsedTime(){returnendTime-startTime;9.7Accont类publicclassDemoA{publicstaticvoidmain(String[]args){Accountaccount=newAccountf);Scannerin=newScanner(System.in);System.out.printlnf'创建用户，依次输入id、balance^annuallnterestRate：H);intid=in.nextlnt();doublebalance=in.nextDouble();doubleannuallnterestRate=in.nextDoublef);account.ChuangJian(id,balance,annuallnterestRate);System.out.printf'请输入取款额：”);intmoney=in.nextlnt();account.\A/ithDraw(money);System.out.printf"请输入存款额:");money=in.nextlnt();account.deposit(money);account.Print();}}classAccount!privateintid;privatedoublebalance;privatedoubleannuallnterestRate;privateDatedateCreated;publicvoidPrint(){System.out.printlnf1余额为:H+balance);System.out.printlnf'月利息为:,,+getMonthlylnterset());System.out.printf'开户日期为:")；getDate();}publicvoidChuangJian(){id=0;balance=0;annuallnterestRate=O;}publicvoidChuangJian(intid,doublebalance,doubleannuallnterestRate){this.id=id;this.balance=balance;this.annuallnterestRate=annuallnterestRate;this.dateCreated=newDate();}publicvoidLook(){System.out.println(Hid："+id);System.out.println(nbalance：H+balance);System.out.println「annuallnterestRate："+annuallnterestRate);publicvoidChangefintid){System.out.printlnf'请输入更改后的id^balance^annuallnterestRate'1);Seanne「in=newScanner(System.in);this.id=in.nextlnt();this,balancedn.nextDouble();this.annuallnterestRate=irunextDoublef);}publicDategetDate(){System.out.println(dateCreated);returndateCreated;}publicdoublegetMonthlylnterestRate(){returnannuallnterestRate/12;}publicdoublegetMonthlylnterset(){returngetMonthlylnterestRate()*balanee;}publicvoidwithDrawfintmoneyOut){balance-=moneyOut;}publicvoiddepos让(intmoneyln){balance+=moneyln;}}，ZC:\ProgramFiles\java\jdk1・8・0_101\bin\java•巳:・・・创建用户，依次输入id、balance、annualInterestRate：请输入取款额：2500请输入存款额：3000余额为；20500.0月利息为：76.875开户日期为：TueOct2218:39:24CST2019Processfinishedwithexitcode09.8Fan类publicclassDemoB{publicstaticvoidmain(String[]args){Fanfanl=newFan();fanl.setSpeed(3);fanl.setRadius(lO);fanl.setColorf^ellow");fanl.setOn(true);System.out.println(,,fabl:"+fanl.toString());Fanfan2=newFan();fan2.setSpeed(2);fan2.setRadius(5);fan2.setColor(,,blueH);fan2.setOn(false);System.out.println(,,fab2:"+fan2.toString());}}classFan{intSLOW=1;intMEDIUM=2;intFAST=3;privateintspeed=SLOW;privatebooleanon=false;privatedoubleradius=5;Stringcolor=,,blue";publicFan(){}publicintgetSpeed(){returnspeed;}publicvoidsetSpeed(intspeed){this.speed=speed;}publicbooleanisOn(){returnon;}publicvoidsetOnfbooleanon){this.on二on;}publicdoublegetRadius(){returnradius;}publicvoidsetRadiusfdoubleradius){this.radius=radius;publicStringgetColor(){returncolor;publicvoidsetColor(Stringcolor){this.color=color;}publicStringtoString(){if(on){returngetSpeed()+,,\t,,+getColor()+,,\t,,+getRadius();}else{return"fanisoff,,+,,\t,,+getColor()+,,\t，，+getRadius();9.11代数：2X2的线性方程publicclassDemoC{publicstaticvoidmain(String[]args){LinearEquationlinearEquationl=newLinearEquation(9,4,3,-5,-6,-21);if(linearEquationl.isSolvable()){System.out.printlnf'X是：”+linearEquationl・getX()+蔦\tY是:,,+linearEquationl.getY());}elseSystem.out.print(HTheequationhasnosolution")；LinearEquationlinearEquation2=newLinearEquation(1,2,2,4,4,5);if(linearEquation2.isSolvable()){System.out.print("X是：,,+linearEquation2.getX()+,,/\tY是：N+linearEquation2.getY());}elseSystem.out.print(HTheequationhasnosolution")；classLinearEquation{privatedoublea;privatedoubleb;pr