Java語言程序設(shè)計(基礎(chǔ)篇)原書第十一版 梁勇 第9章 課后題答案

9.1設(shè)計一個名為Rectangle的類表示矩形publicclassTest{publicstaticvoidmain(String[]args){Rectanglerectanglel=newRectangle(4,40);System.out.println("矩形的寬是"+rectanglel.width+",高是"+rectanglel.height+"z面積是"+rectanglel?getArea()+”，周長是n+rectanglel.getPerimeter());Rectanglerectangle2=newRectangle(3.5,35.9);System.out.print("矩形的寬是"+rectangle2.width+",高是"+rectangle2.height+",面積是,,+rectangle2.getArea()+,1,周長是,,+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〃...矩形的寬是4.0,髙是40.0,面積是160.0,周長是88.0矩形的寬是3?5,高是35.9,面積是125.64999999999999,周長是78?8Processfinishedwithexitcode09.3使用Date類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類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"測試所用時間為:"+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測試所用時間為;12406msProcessfinishedwithexitcode}publiclonggetElapsedTime(){returnendTime-startTime;9.7Accont類publicclassDemoA{publicstaticvoidmain(String[]args){Accountaccount=newAccountf);Scannerin=newScanner(System.in);System.out.printlnf'創(chuàng)建用戶，依次輸入id、balance^annuallnterestRate：H);intid=in.nextlnt();doublebalance=in.nextDouble();doubleannuallnterestRate=in.nextDoublef);account.ChuangJian(id,balance,annuallnterestRate);System.out.printf'請輸入取款額：”);intmoney=in.nextlnt();account.\A/ithDraw(money);System.out.printf"請輸入存款額:");money=in.nextlnt();account.deposit(money);account.Print();}}classAccount!privateintid;privatedoublebalance;privatedoubleannuallnterestRate;privateDatedateCreated;publicvoidPrint(){System.out.printlnf1余額為:H+balance);System.out.printlnf'月利息為:,,+getMonthlylnterset());System.out.printf'開戶日期為:")；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'請輸入更改后的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讓(intmoneyln){balance+=moneyln;}}，ZC:\ProgramFiles\java\jdk1?8?0_101\bin\java?巳:???創(chuàng)建用戶，依次輸入id、balance、annualInterestRate：請輸入取款額：2500請輸入存款額：3000余額為；20500.0月利息為：76.875開戶日期為：TueOct2218:39:24CST2019Processfinishedwithexitcode09.8Fan類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代數(shù)：2X2的線性方程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