《Java语言程序设计基础篇》第10版 梁勇 著第十章练习题答案.docx
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《Java语言程序设计基础篇》第10版梁勇著第十章练习题答案
《Java语言程序设计（基础篇）》（第10版梁勇著）
第十章练习题答案
10.1
publicclassExercise10_01{
publicstaticvoidmain（String[]args）{
Timetime1=newTime（）;
System.out.println（"Hour:
"+time1.getHour（）+"Minute:
"+
time1.getMinute（）+"Second:
"+time1.getSecond（））;
Timetime2=newTime（555550000）;
System.out.println（"Hour:
"+time2.getHour（）+"Minute:
"+
time2.getMinute（）+"Second:
"+time2.getSecond（））;
}
}
classTime{
privateinthour;
privateintminute;
privateintsecond;
publicTime（）{
this（System.currentTimeMillis（））;
}
publicTime（longelapsedTime）{
setTime（elapsedTime）;
}
publicTime（inthour,intminute,intsecond）{
this.hour=hour;
this.minute=minute;
this.second=second;
}
publicintgetHour（）{
returnhour;
}
publicintgetMinute（）{
returnminute;
}
publicintgetSecond（）{
returnsecond;
}
publicvoidsetTime（longelapsedTime）{
//Obtainthetotalsecondssincethemidnight,Jan1,1970
longtotalSeconds=elapsedTime/1000;
//Computethecurrentsecondintheminuteinthehour
second=（int）（totalSeconds%60）;
//Obtainthetotalminutes
longtotalMinutes=totalSeconds/60;
//Computethecurrentminuteinthehour
minute=（int）（totalMinutes%60）;
//Obtainthetotalhours
inttotalHours=（int）（totalMinutes/60）;
//Computethecurrenthour
hour=（int）（totalHours%24）;
}
}
10.2
publicclassExercise10_02{
publicstaticvoidmain（String[]args）{
BMIbmi1=newBMI（"JohnDoe",18,145,5,10）;
System.out.println（"TheBMIfor"+bmi1.getName（）+"is"
+bmi1.getBMI（）+""+bmi1.getStatus（））;
BMIbmi2=newBMI（"PeterKing",215,5,10）;
System.out.println（"TheBMIfor"+bmi2.getName（）+"is"
+bmi2.getBMI（）+""+bmi2.getStatus（））;
}
staticclassBMI{
privateStringname;
privateintage;
privatedoubleweight;//inpounds
privatedoubleheight;//ininches
publicfinaldoubleKILOGRAMS_PER_POUND=0.45359237;
publicfinaldoubleMETERS_PER_INCH=0.0254;
/**ConstructaBMIwiththespecifiedname,age,weight,
*feetandinches
*/
publicBMI（Stringname,intage,doubleweight,doublefeet,doubleinches）{
this.name=name;
this.age=age;
this.weight=weight;
this.height=feet*12+inches;
}
publicBMI（Stringname,intage,doubleweight,doubleheight）{
this.name=name;
this.age=age;
this.weight=weight;
this.height=height;
}
publicBMI（Stringname,doubleweight,doubleheight）{
this（name,20,weight,height）;
}
publicdoublegetBMI（）{
doublebmi=weight*KILOGRAMS_PER_POUND/
（（height*METERS_PER_INCH）*（height*METERS_PER_INCH））;
returnMath.round（bmi*100）/100.0;
}
publicStringgetStatus（）{
doublebmi=getBMI（）;
if（bmi<16）
return"seriouslyunderweight";
elseif（bmi<18）
return"underweight";
elseif（bmi<24）
return"normalweight";
elseif（bmi<29）
return"overweight";
elseif（bmi<35）
return"seriouslyoverweight";
else
return"gravelyoverweight";
}
publicStringgetName（）{
returnname;
}
publicintgetAge（）{
returnage;
}
publicdoublegetWeight（）{
returnweight;
}
publicdoublegetHeight（）{
returnheight;
}
}
}
10.3
publicclassExercise10_03{
publicstaticvoidmain（String[]args）{
MyIntegern1=newMyInteger（5）;
System.out.println（"n1iseven?
"+n1.isEven（））;
System.out.println（"n1isprime?
"+n1.isPrime（））;
System.out.println（"15isprime?
"+MyInteger.isPrime（15））;
char[]chars={'3','5','3','9'};
System.out.println（MyInteger.parseInt（chars））;
Strings="3539";
System.out.println（MyInteger.parseInt（s））;
MyIntegern2=newMyInteger（24）;
System.out.println（"n2isodd?
"+n2.isOdd（））;
System.out.println（"45isodd?
"+MyInteger.isOdd（45））;
System.out.println（"n1isequalton2?
"+n1.equals（n2））;
System.out.println（"n1isequalto5?
"+n1.equals（5））;
}
}
classMyInteger{
privateintvalue;
publicintgetValue（）{
returnvalue;
}
publicMyInteger（intvalue）{
this.value=value;
}
publicbooleanisPrime（）{
returnisPrime（value）;
}
publicstaticbooleanisPrime（intnum）{
if（（num==1）||（num==2））{
returntrue;
}
for（inti=2;i<=num/2;i++）{
if（num%i==0）{
returnfalse;
}
}
returntrue;
}
publicstaticbooleanisPrime（MyIntegero）{
returnisPrime（o.getValue（））;
}
publicbooleanisEven（）{
returnisEven（value）;
}
publicbooleanisOdd（）{
returnisOdd（value）;
}
publicstaticbooleanisEven（intn）{
returnn%2==0;
}
publicstaticbooleanisOdd（intn）{
returnn%2!
=0;
}
publicstaticbooleanisEven（MyIntegern）{
returnisEven（n.getValue（））;
}
publicbooleanequals（intanotherNum）{
returnvalue==anotherNum;
}
publicbooleanequals（MyIntegero）{
returnvalue==o.getValue（）;
}
publicstaticintparseInt（char[]numbers）{
//numbersconsistsofdigitcharacters.
//Forexample,ifnumbersis{'1','2','5'},thereturnvalue
//shouldbe125.Pleasenotethat
//numbers[0]is'1'
//numbers[1]is'2'
//numbers[2]is'5'
intresult=0;
for（inti=0;iresult=result*10+（numbers[i]-'0'）;
}
returnresult;
}
//YoumaymentionthiswhenyoucoveredCh8
publicstaticintparseInt（Strings）{
//sconsistsofdigitcharacters.
//Forexample,ifsis"125",thereturnvalue
//shouldbe125.
intresult=0;
for（inti=0;iresult=result*10+（s.charAt（i）-'0'）;
}
returnresult;
}
}
10.4
publicclassExercise10_04{
publicstaticvoidmain（String[]args）{
MyPointp1=newMyPoint（）;
MyPointp2=newMyPoint（10,30.5）;
System.out.println（p1.distance（p2））;
System.out.println（MyPoint.distance（p1,p2））;
}
}
classMyPoint{
privatedoublex;
privatedoubley;
publicMyPoint（）{
}
publicMyPoint（doublex,doubley）{
this.x=x;
this.y=y;
}
publicdoubledistance（MyPointsecondPoint）{
returndistance（this,secondPoint）;
}
publicstaticdoubledistance（MyPointp1,MyPointp2）{
returnMath.sqrt（（p1.x-p2.x）*（p1.x-p2.x）+（p1.y-p2.y）
*（p1.y-p2.y））;
}
publicdoublegetX（）{
returnx;
}
publicdoublegetY（）{
returny;
}
}
10.5
publicclassExercise10_05{
publicstaticvoidmain（String[]args）{
StackOfIntegersstack=newStackOfIntegers
（2）;
java.util.Scannerinput=newjava.util.Scanner（System.in）;
//Prompttheusertoenteraninteger
System.out.print（"Enteraninteger:
"）;
//Convertstringtoint
intnumber=input.nextInt（）;
System.out.println（"Thefactorsfor"+number+"is"）;
//Findandstoreallthesmallestfactorsoftheinteger
intfactor=2;
while（factor<=number）{
if（number%factor==0）{
number=number/factor;
stack.push（factor）;
}
else{
factor++;
}
}
//Displayfactors
while（!
stack.empty（））{
System.out.print（stack.pop（）+""）;
}
}
}
10.6
publicclassExercise10_06{
publicstaticvoidmain（String[]args）{
finalintLIMIT=120;
intcount=0;
StackOfIntegersstack=newStackOfIntegers（）;
//Repeatedlyfindprimenumbers
for（intnumber=2;numberif（isPrime（number））{
stack.push（number）;
count++;//Increasetheprimenumbercount
}
//Printthefirst30primenumbersindecreasingorder
System.out.println（"Theprimenumberslessthan120are\n"）;
finalintNUMBER_PER_LINE=10;
while（!
stack.empty（））{
System.out.print（stack.pop（）+""）;
if（stack.getSize（）%NUMBER_PER_LINE==0）
System.out.println（）;//advancetothenewline
}
}
publicstaticbooleanisPrime（intnumber）{
//Assumethenumberisprime
booleanisPrime=true;
//Exercise03_21ifnumberisprime
for（intdivisor=2;divisor<=number/2;divisor++）{
//Iftrue,thenumberisnotprime
if（number%divisor==0）{
//SetisPrimetofalse,ifthenumberisnotprime
isPrime=false;
break;//Exittheforloop
}
}
returnisPrime;
}
}
10.7
publicclassExercise10_07{
//Createtenaccounts
privateAccount[]accounts=newAccount[10];
publicExercise10_07（）{
for（inti=0;iaccounts[i]=newAccount（）;
accounts[i].setId（i）;
accounts[i].setBalance（100）;
}
continueATM:
while（true）{
System.out.print（"Enteranid:
"）;
id=input.nextInt（）;
if（id<1||id>10）{
System.out.println（"Pleaseenteracorrectid"）;
continue;
}
while（true）{
intchoice=getAChoice（）;
switch（choice）{
case1:
System.out.println（"Thebalanceis"+
accounts[id].getBalance（））;
break;
case2:
withdraw（）;
break;
case3:
deposit（）;
break;
case4:
//Youcanrewritethecodewithoutusingthecontinue.
//Todoso,introduceabooleanvariabletocontrolone
//customersession
continuecontinueATM;
}
}
}
}
privatestaticjava.util.Scannerinput=newjava.util.Scanner（System.in）;
intid;
publicstaticvoidmain（String[]args）{
newExercise10_07（）;
}
publicvoidwithdraw（）{
System.out.print（"Enteranamounttowithdraw:
"）;
intamount=input.nextInt（）;
if（amount<=accounts[id].getBalance（））{
accounts[id].withdraw（amount）;
}
else{
System.out.print（"Theamountistoolarge,ignored"）;
}
}
publicvoiddeposit（）{
System.out.print（"Enteranamounttodeposit:
"）;
intamount=input.nextInt（）;
if（amount>=0）{
accounts[id].deposit（amount）;
}
else{
System.out.print（"Theamountisnegative,ignored"）;
}
}
publicintgetAChoice（）{
intchoice;
while（true）{
System.out.println（"\nMainmenu"）;
System.out.println（"1:
checkbalance"）;
System.out.println（"2:
withdr
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