数字转换为英文
输入为int型非负数，最大值为2^31 - 1 = 2 147 483 647
输出为String英文，最大输出为Two Billion One Hundred Forty Seven Million Four Hundred Eighty Three Thousand Six Hundred Forty Seven
输出要求每个单词首字母大写，之间用空格隔开，不需要用“and”做连词
例如：
123 -> "One Hundred Twenty Three" 12345 -> "Twelve Thousand Three Hundred Forty Five" 1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"
处理思路
观察数字2 147 483 647，可以看出由4段组成；每段都是0到999的数字
尝试将数字分段处理；截取每段数字，写专门的函数处理0~999的数字；最后将它们连接起来
编制String数组存放需要的数字；需要时从数组中取用
完整Java代码如下：
1 /** 2 * 3 * @author Rust Fisher 4 * biggest number = 2 147 483 648 - 1 5 * Two Billion One Hundred Forty Seven Million Four Hundred Eighty Three Thousand Six Hundred Forty Seven 6 */ 7 public class Int2Eng { 8 public static String numberToWords(int num) { 9 String result = ""; 10 int inputNum = num; 11 if (num == 0) { 12 result = "Zero"; 13 return result; 14 } 15 16 if (inputNum/1000 == 0 ) {//0 < num < 1000 17 return getThousand(inputNum%1000);// 处理 xxx 18 } 19 20 result = getThousand(inputNum%1000); 21 inputNum = inputNum/1000; //Rust:cut the tail 2 147 483 xxx 22 23 if (inputNum/1000 == 0) { // 1000 <= num < 1 000 000 24 if (result.equals("")) { 25 return (getThousand(inputNum%1000) + " Thousand"); 26 } else { 27 return (getThousand(inputNum%1000) + " Thousand " + result); 28 } 29 } else {// 1 000 000 < num 30 if (result.equals("") && inputNum%1000 == 0) { 31 result = getThousand(inputNum%1000);//do nothing 32 } else if (!result.equals("") && inputNum%1000 != 0){ 33 result = getThousand(inputNum%1000) + " Thousand " + result; 34 } else if (result.equals("") && inputNum%1000 != 0) { 35 result = getThousand(inputNum%1000) + " Thousand" + result; 36 } 37 } 38 39 inputNum = inputNum/1000; 40 if (inputNum/1000 == 0) {//1 000 000 <= num < 1 000 000 000 41 if (result.equals("")) { 42 return (getThousand(inputNum%1000) + " Million"); 43 } else { 44 return (getThousand(inputNum%1000) + " Million " + result); 45 } 46 } else { 47 if (result.equals("") && inputNum%1000 == 0) { 48 result = getThousand(inputNum%1000); 49 } else if (!result.equals("") && inputNum%1000 != 0){ 50 result = getThousand(inputNum%1000) + " Million " + result; 51 } else if (result.equals("") && inputNum%1000 != 0) { 52 result = getThousand(inputNum%1000) + " Million" + result; 53 } 54 } 55 56 inputNum = inputNum/1000; 57 if (result.equals("")) { 58 if (inputNum == 1) { 59 return ("One"+ " Billion"); 60 } else if (inputNum == 2) { 61 return ("Two"+ " Billion"); 62 } 63 } else { 64 if (inputNum == 1) { 65 return ("One"+ " Billion " + result); 66 } else if (inputNum == 2) { 67 return ("Two"+ " Billion " + result); 68 } 69 } 70 return result; 71 } 72 73 public static String getThousand(int input) { 74 String MaxNum = "Two Billion One Hundred Forty Seven Million" + 75 " Four Hundred Eighty Three Thousand Six Hundred Forty Eight"; 76 String single[] = {"Zero", "One", "Two", "Three", "Four", "Five", "Six", 77 "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", 78 "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"}; 79 String tens[] = {"Twenty","Thirty","Forty","Fifty","Sixty","Seventy","Eighty","Ninety"}; 80 81 String output = ""; 82 83 int res1 = input%1000; 84 if (res1/100 != 0) { 85 output = output + single[res1/100] + " Hundred"; 86 } 87 res1 = res1%100;// 1~99 88 89 if (res1 == 0) { 90 // do nothing 91 } else if (res1 < 20) { 92 if (output.equals("")) { 93 output = output + single[res1]; 94 } else { 95 output = output + " " + single[res1]; 96 } 97 return output; 98 } else if (res1 >= 20) { 99 if (output.equals("")) { 100 output = tens[res1/10 - 2]; 101 } else { 102 output = output + " " + tens[res1/10 - 2]; 103 } 104 } 105 106 res1 = res1%10; 107 if (res1 == 0) { 108 109 } else { 110 output = output + " " +single[res1]; 111 } 112 return output; 113 } 114 115 public static void main(String args[]) { 116 117 System.out.println(numberToWords(2127483622)); 118 System.out.println(numberToWords(12)); 119 System.out.println(numberToWords(3555000)); 120 System.out.println(numberToWords(1000)); 121 System.out.println(numberToWords(1000000)); 122 System.out.println(numberToWords(2000000010)); 123 124 } 125 }
输出：
Two Billion One Hundred Twenty Seven Million Four Hundred Eighty Three Thousand Six Hundred Twenty Two
Twelve
Three Million Five Hundred Fifty Five Thousand
One Thousand
One Million
Two Billion Ten
整个程序是顺序执行的，条件合适时即返回结果
