Java-第六章程序清单

1、习题6.2求一个整数各位数之和import java.util.Sca nner;public class sumlf public static void main( Str in gargs ) / TODOAuto-ge nerated method stubSystem. out .print(请输入一个整数：)；Sca nnerin put = new Sca nn er(System.in );long n = in put .n ext In t();(n);System. out .print(输入的整数i= + n + 的各个数字的和是 + sumDigitspublic s

2、tatic long sumDigits( long k)long sum = 0;while ( k != 0) sum += k % 10;k /= 10;return sum;习题6.4 反向显示一个整数import java.util.Sca nner;public class reverse public static void main( Str in gargs ) / TODOAuto-ge nerated method stubSystem. out .print( 请输入一个整数)；Scanner in put = new Scann er(System. in );int

3、 n umberl = in put .n extl nt();reverse ( numberl );public static int reverse( int _number)_int i ;number %10);while (number != 0)System. out .print( number /= 10;return 0;习题6.6 显示图案，此方法只能在10以内对其import java.util.*;public classdisplayPatter n1 public static void main( Str in gargs ) / TODOAuto-ge ner

4、ated method stubSystem. out .print(请输入一个整数)；Scanner in put = new Scann er(System. in );int n = in put .n extI nt();displayPatter n (n);public static void displayPattern(int i ) for (int j = 1; j = i ; j +) for (int k = 0; k = 10)System.out.pri nt();for (int k = j ; k 0;k-) System. out .print( k + );

5、System. out .println();程序清单6-1 调用max方法public class TestMax args ) public static void main(String/ TODOAuto-ge nerated method stub int i = 5;int j = 2;int k = max( i , j );System. out .println(the maxinum of + i + and + j + is + k);public static int max( int num1, int num2) int result ;if ( num1 num2

6、)result = num1;elseresult = num2;return result ; 程序清单 6-2void 方法例如，打印给定分数的等级public class TestVoidMethod public staticvoidmain(String args ) / TODOAuto-generated method stubSystem. out.print(The grade is );printGrade(78.5);System. out.print(The grade is );printGrade(59.5);public static void printGrad

7、e( double score ) if ( score =90.0) System. out .println( A );else if ( score =80.0) System. out .println( B );else if ( score =70.0) System. out .println( C );else if ( score =60.0) System. out .println( D );else System. out .println( F );程序清单 6-3void 方法的例如，与程序清单做比照，打印一个分数的等级 public class TestRetur

8、nVoidMethod public static void main(String args ) System. out .print( The frade is + getGrade (78.5);System. out .print( nThe frade is + getGrade (59.5);publicstaticchargetGrade( double score ) if (score= 90)returnA ;elseif (score= 80)returnB ;elseif (score= 70)returnC ;elseif (score= 60)returnD ;el

9、sereturnF ;程序清单6-4通过传值进行参数传递public class Increment public static void main(String args ) / TODOAuto-generated method stubint x = 1;System. out .println( Before the call, x is + x); increment ( x);System. out .println( After the call, x is + x); public static void increment( int n) n+;System. out .pr

10、intln( n inside the method is + n); 程序清单6-5按值传递参数public class TestPassByValue public static void main( Str in gargs ) / TODOAuto-ge nerated method stubint n um2 = 2;System. out .println(n um1 + and n um2 is int n um1 = 1;Before invoking the swap method, num1 is + num2);After in vok ing the swap meth

11、od, n um1 is + num2);swap( num1, num2);System. out .println( n um1 + and n um2 public staticvoid swap(int n1 , int n2) System. out.pri ntl n(tIside the method);System. out.pri ntl n(ttBefore swapp ing, n1 is + n1 + and n2 is + n2);int temp =n1 ;n1 =n2;n2 = temp ;System. out.pri ntl n(ttAfter swappi

12、ng, n1 is + n1 + and n2 is + n2);程序清单6-6程序模块化_求最大公约数import java.util.Sca nner;public class GreatestCom mon DivisorMethod public static void main( Str in gargs ) / TODOAuto-ge nerated method stubSca nnerin put = new Sca nn er(System.in );System. out .print(Enter first integer:);int n1 = in put .n ext

13、 In t();System. out .print(Enter scond integer:);int n2 = in put .n ext In t();System. out .pri ntl n(The greatest com mon divisor for + n1 + and + n2 + is + gcd ( n1 , n2);public static int gcd( int n1, int n2) intgcd=1；intk =2；while(k = n1&k =n2) if (n 1 % k=0&n2 % k = 0)gcd =卜；k+;return gcd ;程序清单

14、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public class PrimeNumberMethod public static void main( Str in g args ) / TODOAuto-ge nerated method stub);System. out .println(The first 50 prime numbers are nprin tprimeNumbers(50);publicstaticvoid printprimeNumbers(int numberOfPrimes ) finalintNUMBER_OF_PRIMES_PER_LIN

15、E= 10;intcou nt=0;int n umber = 2;while (count numberOfPrimes ) if (isPrime ( number) cou nt +;if (count % NUMBER_OF_PRIMES_PER_LINE= 0) System. out .printf(%-5sn , number);elseSystem. out .printf( %-5s , number );n umber +;publicstaticboolea n isPrime (intn umber)for(int divisor = 2;divisor = numbe

16、r / 2 ;divisor +) if ( number % divisor = 0)return false ;return true程序清单6-8将16进制转换为十进制import java.util.Sca nner;public class Hex2Dec public static void main( Str in gargs ) / TODOAuto-ge nerated method stubScanner in put = new Scann er(System. in );System. out .print(Enter a hex number:Stringhex =

17、in put .nextLine(); /Sting);是什么，in put. nextL ine又是什么System. out .println( The decimal value for hex number + hex + is + hexToDecimal (hex .toUpperCase();public static int hexToDecimal(Str inghex) int decimalValue = 0;for (int i = 0; i =A&ch returndouble max( num2)n um1;doublen um1,double n um2) els

18、ereturnn um2;publicreturnstaticdouble max( max( max( num1,doublen um2),n um1,n um3);double n um2, doublenum3) 程序清单6-10生成随机字符public classRan domCharacter public staticchar getRandomCharacter(char ch1 , char ch2) return ( char )( ch1 + Math.random () * ( ch2 - ch1 + 1);public static char getRandomLowe

19、rCaseLetter() retur n getRa ndomCharacter (a , z);public static char getRandomUpperCaseLetter() returngetRandomCharacter(A , Z);public static char getRandomDigtCharacter() returngetRandomCharacter(O , 9 );public static char getRandimCharacter() returngetRa ndomCharacter(u0000, uFFFF);程序清单6-11生成随机数，调

20、用了6-10的方法public class TestRa ndomCharacter public static void main( Str in gargs ) / TODOAuto-ge nerated method stubfinalintNUMBER_OF_CHARS 175;finalint CHARS_PER_LINE = 25;for (inti = 0; i NUMBER_OF_CHARS i +) char ch = Ran domCharacter.getRa ndomLowerCaseLetter();if ( i + 1) % CHARS_PER_LINE = 0)S

21、ystem. out .println( ch);elseSystem. out .print( ch);程序清单6-12方法抽象，逐步求精import java.util.Sca nner;public class Prin tCale ndar public static void main( Str in gargs ) / TODOAuto-ge nerated method stubSca nner in put = new Sca nn er(System.in );System. out .print(Enter full yuer (e.g., 2022):);int year

22、 = in put .n extl nt();System. out .print(Enter month as a number between 1 and 12:);int month = in put .n extI nt();printMonth (year , month );public staticvoid printMonth(int year , int month ) prin tMo nthTitle(year , month );prin tMo nthBody(year , mon th );public staticvoid printMonthTitle(int

23、year , intmon th ) System.out.pri ntl n(I!I!+ getM on thName(month ) + + year );System.out.pri ntl n(I! );- );System.out.pri ntl n(Sun Mon Tue Wed Tue Fri Sat);public static String getMonthName(int month ) Str ingmonthName =;switch(mon th ) case1:mon thName =January ; break ;case2:mon thName =Fanuar

24、y ; break ;case3:mon thName =March ; break ;case4:mon thName =April ; break ;case5:mon thName =May ; break ;case6:mon thName =June ; break ;case7:mon thName =July ; break ;case8:mon thName =August ; break ;case9:mon thName =September ; breakcase10mon thName =October ; breakcase11mon thName =November

25、 ; breakcase12mon thName =December ; breakreturnmon thName;publicstatic void printMonthBody( int year , int month ) intstartDay = getStartDay (year , month );int n umberOfDays InMon th= getNumberOfDaysl nMonth (year , mon th );int i = 0;for (i = 0;System.for (i = 0;i startDay ; i +) out .print();i = numberOfDaysInMonth;i+) System. out .printf( %4d , i );if ( i + startDay ) % 7 = 0)System. out .println();System. out