1 package com.jdk7.chapter5;
2
3 import java.security.MessageDigest;
4 import java.security.NoSuchAlgorithmException;
5
6 public class PassWord {
7 //该字符串数组元素与转换后的十六进制数一一对应
8 private static String[] nums =
new String[] {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a"
,
9 "b", "c", "d", "e", "f"
};
10
11 /**
12 * 1.将加密字符串分解为byte[]
13 * 2.调用java.security.MessageDigest的静态方法获取对象，再调用实例方法digest将分解的byte[]生成对应的长度为16的byte[]
14 * 3.将长度为16的byte[]转换为十六进制
15 * 4.将数组中每个byte类型值转换为十六进制，从而实现byte[]全部转换为十六进制
16 * 5.将转换后的十六进制字符串拼接
17 * @param str
18 * @return
19 * @throws NoSuchAlgorithmException
20 */
21 public static String createPassword(String str)
throws NoSuchAlgorithmException{
22 byte[] b =
str.getBytes();
23 for(
int i=0;i<b.length;i++
){
24 System.out.print(b[i]+" "
);
25 }
26 System.out.println();
27 byte[] bt = MessageDigest.getInstance("MD5"
).digest(b);
28
29 for(
int i=0;i<bt.length;i++
){
30 System.out.print(bt[i]+" "
);
31 }
32 System.out.println();
33
34 String results =
byteArrayToHexString(bt).toUpperCase();
35 return results;
36 }
37
38 private static String byteArrayToHexString(
byte[] bt) {
39 StringBuffer sb =
new StringBuffer();
40 for(
int i=0;i<bt.length;i++
){
41 sb.append(byteToHexString(bt[i]));
42 }
43 return sb.toString();
44 }
45
46 /**
47 * byte和int类型间相互转换，int范围基于[-256,256]
48 * int类型强制转换为byte时，如int i值大于127则自减256; 如果范围为int i为[0,127]，则取i对应的值 ; 如果int i在[-256,-128)则自加256 ;如果int i为[-128,0]则取i对应的值
49 * 续上：byte再转换为int时，如byte b小于等于零则自加256; 如果范围为int i为(0,127]
50 * @param b
51 * @return
52 */
53 private static String byteToHexString(
byte b) {
54 int n =
b;
55 //该规则主要是int类型转换为byte类型规则的逆向
56 if(n<=0
){
57 n = n+256
;
58 }
59 byte b1 = (
byte)n;
60 int d1 = n / 16
;
61 int d2 = n % 16
;
62 return nums[d1]+
nums[d2];
63 }
64
65 public static void main(String[] args)
throws NoSuchAlgorithmException {
66 System.out.println(PassWord.createPassword("celineluo"
));
67 System.out.println(PassWord.createPassword("celineluo1"
));
68 }
69 }
70
71
72 执行结果：
73 99 101 108 105 110 101 108 117 111
74 -75 -39 -40 -73 53 113 -16 -97 26 104 -34 -2 105 13 -120 -120
75 B5D9D8B73571F09F1A68DEFE690D8888
76 99 101 108 105 110 101 108 117 111 49
77 53 -97 -35 83 102 21 53 -52 33 76 67 -117 -28 125 -80 -34
78 359FDD53661535CC214C438BE47DB0DE
转载于:https://www.cnblogs.com/celine/p/8467559.html
