Java语言程序设计-基础篇-第八版-第五章

 1 package chapter5方法;
 2 //求最大公约数；
 3 public class GreatestCommonDivisor {
 4     public static void main(String[] args){
 5         java.util.Scanner input = new java.util.Scanner(System.in);
 6         
 7         System.out.print("Enter first integer: ");
 8         int n1 = input.nextInt();
 9         System.out.print("Enter second integer: ");
10         int n2 = input.nextInt();
11         System.out.println("The greatest common divisor for " + n1 +
12                 " and " + n2 + " is " + gcd(n1, n2));
13     }
14     
15     public static int gcd(int n1, int n2){
16         int gcd = 1;
17         int k = 2;
18         while(k <= n1 && k <= n2){           
19             if (n1 % k == 0 && n2 % k ==0)   //能同时被n1和n2整除；
20                 gcd = k;
21             k++;
22         }
23         return gcd;
24     }
25 }

 1 package chapter5方法;
 2 
 3 public class Increment {
 4     public static void main(String[] args){
 5         int x = 1;
 6         System.out.println("Befre the call, x is " + x);
 7         increment(x);
 8         System.out.println("After the call, x is " + x);
 9     }
10     
11     public static void increment(int n) {
12         n++;
13         System.out.println("n inside the method is " + n);
14     }
15 
16 }

 1 package chapter5方法;
 2 
 3 public class PrimeNumberMethod {
 4     public static void main(String[] args){
 5         System.out.println("The first 50 prime numbers are \n");
 6         printPrimeNumbers(50);
 7     }
 8    
 9     public static void printPrimeNumbers(int numberOfPrimes){
10         final int NUMBER_OF_PRIMES_PER_LINE = 10;
11         int count = 0;
12         int number = 2;
13         
14         while (count < numberOfPrimes) {
15             if (isPrime(number)) {
16                 count++;
17                 if (count % NUMBER_OF_PRIMES_PER_LINE == 0) {
18                     System.out.printf("%-5s\n", number);   
19                 }
20                 else 
21                     System.out.printf("%-5s", number);
22             }
23             number++;
24         }
25     }
26     
27     public static boolean isPrime(int number){
28         for(int divisor = 2; divisor <= number /2; divisor++) {
29             if (number % divisor == 0){
30                 return false;
31             }
32         }
33         return true;
34     }
35        
36 }

 1 package chapter5方法;
 2 
 3 public class TestMax {
 4     public static void main(String[] args){
 5         int i = 5;
 6         int j = 2;
 7         int k = max(i, j);
 8         System.out.println("The maximum between " + i + 
 9                 " and " + j + " is " + k);
10     }    
11         public static int max(int num1, int num2){
12             int result;
13             if (num1 > num2)
14                 result = num1;
15             else
16                 result = num2;
17             return result;
18         }
19 }

 

 1 package chapter5方法;
 2 
 3 public class TestPassByValue {
 4     public static void main(String[] args){
 5           int num1 = 1;
 6           int num2 = 2;
 7           System.out.println("Before invoking the swap method, num1 is " +
 8            num1 + " and num2 is " + num2);
 9           swap(num1, num2);
10           System.out.println("After invoking the swap method, num1 is " + 
11            num1 + " and num2 is " + num2);
12     }
13     
14     public static void swap(int n1, int n2){
15         System.out.println("\tInside the swap method");
16         System.out.println("\t\tBefore swapping n1 is " + 
17          n1 + " n2 is " + n2);
18         
19         int temp = n1;
20         n1 = n2;
21         n2 = temp;
22         
23         System.out.println("\t\tAfter swapping n1 is " + 
24          n1 + " n2 is " + n2);
25     }
26 }

 1 package chapter5方法;
 2 
 3 public class TestReturnGradeMethod {
 4     public static void main(String[]args){
 5         System.out.print("The grade is " + getGrade(78.6));
 6         System.out.print("\nThe grade is " + getGrade(59.8));
 7     }
 8     
 9     public static char getGrade(double score) {
10         if (score >= 90.0)
11             return 'A';
12         else if (score >= 80.0)
13             return 'B';
14         else if (score >= 70.0)
15             return 'C';
16         else if (score >= 60.0)
17             return 'D';
18         else 
19             return 'F';
20     }
21 
22 }

 1 package chapter5方法;
 2 
 3 public class TestViodMethod {
 4     public static void main(String[] args){
 5           System.out.print("The grade is ");
 6           printGrade(78.5);
 7           
 8           System.out.print("The grade is ");
 9           printGrade(59.7);
10     }
11 
12     public static void printGrade(double score) {
13         if (score >= 90.0){
14             System.out.println('A');
15         }
16         else if (score >= 80.0){
17             System.out.println('B');
18         }
19         else if (score >= 70.0){
20             System.out.println('C');
21         }
22         else if (score >= 60.0){
23             System.out.println('D');
24         }
25         else{
26             System.out.println('F');
27         }
28     }
29 }

 

 1 package chapter5方法;
 2 import java.util.*;//十进制转换为十六进制！
 3 public class Decimal2HexConversion {
 4     public static void main(String[] args){
 5         Scanner input = new Scanner(System.in);
 6         System.out.print("Enter a decimal number: ");
 7         int decimal = input.nextInt();
 8         
 9         System.out.println("The hex number for decimal " + 
10            decimal + " is " + decimalToHex(decimal));
11     }
12     
13     public static String decimalToHex(int decimal) {
14         String hex = "";
15         
16         while (decimal != 0) {
17             int hexValue = decimal % 16;
18             hex = toHexChar(hexValue) + hex;
19             decimal = decimal / 16;
20         }
21         return hex;
22     }
23     
24     public static char toHexChar(int hexValue) {
25         if (hexValue <= 9 && hexValue >= 0)
26             return (char)(hexValue + '0');
27         else
28             return (char)(hexValue - 10 + 'A');
29     }
30 }

 1 package chapter5方法;
 2 import java.util.*;
 3 public class PrintCalendar {
 4     
 5     public static void main(String[] args) {
 6         Scanner input = new Scanner(System.in);
 7         System.out.print("Eneter full year (e.g.,2001): ");
 8         int year = input.nextInt();
 9         System.out.print("Eneter nonth in number between 1 an 12: ");
10         int month = input.nextInt();
11         
12         printMonth(year, month);
13     }
14     
15     public static void printMonth(int year, int month){
16         printMonthTitle(year, month);
17         printMonthBody(year, month);
18     }
19     
20     public static void printMonthTitle(int year, int month){
21         System.out.println("         " + getMonthName(month) + " " + year);
22         System.out.println("----------------------------");
23         System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
24     }
25     
26     public static String getMonthName(int month){
27         String monthName = "";
28         switch (month) {
29         case 1:monthName = "January"; break;
30         case 2:monthName = "February"; break;
31         case 3:monthName = "March"; break;
32         case 4:monthName = "April"; break;
33         case 5:monthName = "May"; break;
34         case 6:monthName = "June"; break;
35         case 7:monthName = "July"; break;
36         case 8:monthName = "August"; break;
37         case 9:monthName = "Septemper"; break;
38         case 10:monthName = "October";break;
39         case 11:monthName = "November"; break;
40         case 12:monthName = "December";
41         }
42         return monthName;
43     }
44     
45     public static void printMonthBody(int year, int month){
46         int startDay = getStartDay(year, month);
47         int numberOfDaysInMonth = getNumberOfDaysInMonth(year, month);
48         
49         int i = 0;
50         for (i = 0; i < startDay; i++)
51             System.out.print("   ");
52         
53         for (i = 1; i <= numberOfDaysInMonth; i++){
54             System.out.printf("%4d", i);
55             if ((i + startDay) % 7 == 0)
56                 System.out.println();
57         }
58         System.out.println();
59     }
60     
61     public static int getStartDay(int year, int month){
62         final int START_DAY_FOR_JAN_1_1800 = 3;
63         int totalNumberOfDays = getTotalNumberOfDays(year, month);
64         return (totalNumberOfDays + START_DAY_FOR_JAN_1_1800) % 7;
65     }
66     
67     public static int getTotalNumberOfDays(int year, int month){
68         int total = 0;
69         for (int i = 1800; i < year; i++)
70             if(isLeapYear(i))
71                 total = total + 366;
72             else
73                 total = total + 365;
74         
75         for (int i = 1; i < month; i++)
76             total = total + getNumberOfDaysInMonth(year, i);
77         
78         return total;
79     }
80     
81     public static int getNumberOfDaysInMonth(int year, int month){
82         if (month == 1 || month == 3 || month == 5 || month == 7 || 
83             month == 8 || month == 10 || month == 12)
84             return 31;
85         if (month == 4 || month == 6 ||month == 9 || month ==  11)
86             return 30;
87         if (month == 2) return isLeapYear(year) ? 29 : 28;
88         return 0;
89     }
90     
91     public static boolean isLeapYear(int year){
92         return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
93     }
94 }

 1 package chapter5方法;
 2 
 3 public class RandomCharacter {
 4     public static char getRandomCharacter(char ch1, char ch2){
 5         return (char)(ch1 + Math.random() * (ch2 - ch1 + 1));
 6     }
 7     
 8     
 9     public static char getRandomLowerCaseLetter(){
10         return getRandomCharacter('a', 'z');
11     }
12     public static char getRandomUpperCaseLetter(){
13         return getRandomCharacter('A', 'Z');
14     }
15     public static char getRandomDigitCharacter(){
16         return getRandomCharacter('0', '9');
17     }
18     public static char getRandomCharcter(){
19         return getRandomCharacter('\u0000', '\uFFFF');
20     }
21 
22 }

 1 package chapter5方法;
 2 
 3 public class TestMethodOverloading {
 4     public static void main(String[] args){
 5         System.out.println("The maximum between 3 and 4 is " + max(3, 4));
 6         System.out.println("The maximun between 3.0 and 5.4 is " + max(3.0, 5.4));
 7         System.out.println("The maximum between 3.0, 5.4, and 10.14 is " + max(3.0, 5.4, 10.14));
 8     }
 9    
10     public static int max(int num1, int num2){
11         if (num1 > num2)
12             return num1;
13         else
14             return num2;
15     }
16     public static double max(double num1, double num2){
17         if (num1 > num2)
18             return num1;
19         else
20             return num2;
21     }
22     
23     public static double max(double num1, double num2, double num3){
24         return max(max(num1, num2), num3);
25     }
26 }

 1 package chapter5方法;
 2 
 3 public class TestRandomCharacter {
 4     public static void main(String args[]){
 5         final int NUMBER_OF_CHARS = 50; //打印的字符数，循环次数；
 6         final int CHARS_PER_LINE = 25;
 7         
 8         for (int i = 0; i < NUMBER_OF_CHARS; i++){
 9             char ch = RandomCharacter.getRandomLowerCaseLetter();
10             if ((i + 1) % CHARS_PER_LINE == 0)
11                 System.out.println(ch); //打印并换行；
12             else
13                 System.out.print(ch + " "); //打印不换行；
14                  
15         }
16     }
17 }

 

转载于:https://www.cnblogs.com/bailun/archive/2013/01/27/2879016.html