Java第六章程序清单.docx
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Java第六章程序清单.docx
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Java第六章程序清单
习题6.2(求一个整数各位数之和)
importjava.util.Scanner;
publicclasssumIf{
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
System.out.print("请输入一个整数:
");
Scannerinput=newScanner(System.in);
longn=input.nextInt();
System.out.print("输入的整数i="+n+"的各个数字的和是"+sumDigits(n));
}
publicstaticlongsumDigits(longk){
longsum=0;
while(k!
=0){
sum+=k%10;
k/=10;
}
returnsum;
}
}
习题6.4(反向显示一个整数)
importjava.util.Scanner;
publicclassreverse{
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
System.out.print("请输入一个整数");
Scannerinput=newScanner(System.in);
intnumber1=input.nextInt();
reverse(number1);
}
publicstaticintreverse(intnumber){
inti;
while(number!
=0){
System.out.print(number%10);
number/=10;
}
return0;
}
}
习题6.6(显示图案,此方法只能在10以内对其)
importjava.util.*;
publicclassdisplayPattern1{
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
System.out.print("请输入一个整数");
Scannerinput=newScanner(System.in);
intn=input.nextInt();
displayPattern(n);
}
publicstaticvoiddisplayPattern(inti){
for(intj=1;j<=i;j++){
for(intk=0;k System.out.print(""); //if(j>=10)System.out.print(""); } for(intk=j;k>0;k--){ System.out.print(k+""); } System.out.println(); } } } 程序清单6-1(调用max方法) publicclassTestMax{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub inti=5; intj=2; intk=max(i,j); System.out.println("themaxinumof"+i+"and"+j+"is"+k); } publicstaticintmax(intnum1,intnum2){ intresult; if(num1>num2) result=num1; else result=num2; returnresult; } } 程序清单6-2(void方法示例,打印给定分数的等级) publicclassTestVoidMethod{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub System.out.print("Thegradeis"); printGrade(78.5); System.out.print("Thegradeis"); printGrade(59.5); } publicstaticvoidprintGrade(doublescore){ if(score>=90.0){ System.out.println('A'); } elseif(score>=80.0){ System.out.println('B'); } elseif(score>=70.0){ System.out.println('C'); } elseif(score>=60.0){ System.out.println('D'); } else{ System.out.println('F'); } } } 程序清单6-3(void方法的示例,与程序清单做对比,打印一个分数的等级) publicclassTestReturnVoidMethod{ publicstaticvoidmain(String[]args){ System.out.print("Thefradeis"+getGrade(78.5)); System.out.print("\nThefradeis"+getGrade(59.5)); } publicstaticchargetGrade(doublescore){ if(score>=90) return'A'; elseif(score>=80) return'B'; elseif(score>=70) return'C'; elseif(score>=60) return'D'; else return'F'; } } 程序清单6-4(通过传值进行参数传递) publicclassIncrement{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub intx=1;; System.out.println("Beforethecall,xis"+x); increment(x); System.out.println("Afterthecall,xis"+x); } publicstaticvoidincrement(intn){ n++; System.out.println("ninsidethemethodis"+n); } } 程序清单6-5(按值传递参数) publicclassTestPassByValue{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub intnum1=1; intnum2=2; System.out.println("Beforeinvokingtheswapmethod,num1is"+ num1+"andnum2is"+num2); swap(num1,num2); System.out.println("Afterinvokingtheswapmethod,num1is"+ num1+"andnum2"+num2); } publicstaticvoidswap(intn1,intn2){ System.out.println("\tIsidethemethod"); System.out.println("\t\tBeforeswapping,n1is"+n1+"andn2is"+n2); inttemp=n1; n1=n2; n2=temp; System.out.println("\t\tAfterswapping,n1is"+n1+"andn2is"+n2); } } 程序清单6-6(程序模块化_求最大公约数) importjava.util.Scanner; publicclassGreatestCommonDivisorMethod{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub Scannerinput=newScanner(System.in); System.out.print("Enterfirstinteger: "); intn1=input.nextInt(); System.out.print("Enterscondinteger: "); intn2=input.nextInt(); System.out.println("Thegreatestcommondivisorfor"+n1+"and"+n2+"is"+gcd(n1,n2)); } publicstaticintgcd(intn1,intn2){ intgcd=1; intk=2; while(k<=n1&&k<=n2){ if(n1%k==0&&n2%k==0) gcd=k; k++; } returngcd; } } 程序清单6-7(程序模块化,打印50以内的素数,输出结果与书上不一致) publicclassPrimeNumberMethod{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub System.out.println("Thefirst50primenumbersare\n"); printprimeNumbers(50); } publicstaticvoidprintprimeNumbers(intnumberOfPrimes){ finalintNUMBER_OF_PRIMES_PER_LINE=10; intcount=0; intnumber=2; while(count if(isPrime(number)){ count++; } if(count%NUMBER_OF_PRIMES_PER_LINE==0){ System.out.printf("%-5s\n",number); } else System.out.printf("%-5s",number); number++; } } publicstaticbooleanisPrime(intnumber){ for(intdivisor=2;divisor<=number/2;divisor++){ if(number%divisor==0) returnfalse; } returntrue; } } 程序清单6-8(将16进制转换为十进制) importjava.util.Scanner; publicclassHex2Dec{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub Scannerinput=newScanner(System.in); System.out.print("Enterahexnumber: "); Stringhex=input.nextLine();//Sting是什么,input.nextLine又是什么 System.out.println("Thedecimalvalueforhexnumber"+hex+"is"+hexToDecimal(hex.toUpperCase())); } publicstaticinthexToDecimal(Stringhex){ intdecimalValue=0; for(inti=0;i charhexChar=hex.charAt(i);//hex.charAt(i)是什么 decimalValue=decimalValue*16+hexCharToDecimal(hexChar); } returndecimalValue; } publicstaticinthexCharToDecimal(charch){ if(ch>='A'&&ch<='F') return10+ch-'A'; else returnch-'0'; } } 程序清单6-9(重载方法,求最大值) publicclassTestMethodOverloading{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub System.out.println("Themaxmumof3and4is"+max(3,4)); System.out.println("Themaxmumof3.0and5.4is"+max(3.0,5.4)); System.out.println("Themaxmumof3.0,4.5and10.14is"+max(3.0,5.4,10.14)); } publicstaticintmax(intnum1,intnum2){ if(num1>num2) returnnum1; else returnnum2; } publicstaticdoublemax(doublenum1,doublenum2){ if(num1>num2) returnnum1; else returnnum2; } publicstaticdoublemax(doublenum1,doublenum2,doublenum3){ returnmax(max(num1,num2),num3); } } 程序清单6-10(生成随机字符) publicclassRandomCharacter{ publicstaticchargetRandomCharacter(charch1,charch2){ return(char)(ch1+Math.random()*(ch2-ch1+1)); } publicstaticchargetRandomLowerCaseLetter(){ returngetRandomCharacter('a','z'); } publicstaticchargetRandomUpperCaseLetter(){ returngetRandomCharacter('A','Z'); } publicstaticchargetRandomDigtCharacter(){ returngetRandomCharacter('0','9'); } publicstaticchargetRandimCharacter(){ returngetRandomCharacter('\u0000','\uFFFF'); } } 程序清单6-11(生成随机数,调用了6-10的方法) publicclassTestRandomCharacter{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub finalintNUMBER_OF_CHARS=175; finalintCHARS_PER_LINE=25; for(inti=0;i charch=RandomCharacter.getRandomLowerCaseLetter(); if((i+1)%CHARS_PER_LINE==0) System.out.println(ch); else System.out.print(ch); } } } 程序清单6-12(方法抽象,逐步求精) importjava.util.Scanner; publicclassPrintCalendar{ publicstaticvoidmain(String[]args){ //TODOAuto-generatedmethodstub Scannerinput=newScanner(System.in); System.out.print("Enterfullyuer(e.g.,2012): "); intyear=input.nextInt(); System.out.print("Entermonthasanumberbetween1and12: "); intmonth=input.nextInt(); printMonth(year,month); } publicstaticvoidprintMonth(intyear,intmonth){ printMonthTitle(year,month); printMonthBody(year,month); } publicstaticvoidprintMonthTitle(intyear,intmonth){ System.out.println(""+getMonthName(month)+""+year); System.out.println("---------------------"); System.out.println("SunMonTueWedTueFriSat"); } publicstaticStringgetMonthName(intmonth){ StringmonthName=""; switch(month){ case1: monthName="January";break; case2: monthName="Fanuary";break; case3: monthName="March";break; case4: monthName="April";break; case5: monthName="May";break; case6: monthName="June";break; case7: monthName="July";break; case8: monthName="August";break; case9: monthName="September";break; case10: monthName="October";break; case11: monthName="November";break; case12: monthName="December";break; } returnmonthName; } publicstaticvoidprintMonthBody(intyear,intmonth){ intstartDay=getStartDay(year,month); intnumberOfDaysInMonth=getNumberOfDaysInMonth(year,month); inti=0; for(i=0;i System.out.print(""); } for(i=0;i<=numberOfDaysInMonth;i++){ System.out.printf("%4d",i); if((i+startDay)%7==0) System.o
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