在网上查到的md5算法的实现，记录一下。
方法一：
public class MD5 {
private static MD5 md5;
private MD5()
{
}
public static MD5 getInstance() {
if (md5 == null) {
md5 = new MD5();
}
return md5;
}
/*
* Convert a 32-bit number to a hex string with ls-byte first
*/
private String hex_chr = "0123456789abcdef";
private String rhex(int num) {
String str = "";
for (int j = 0; j <= 3; j++)
str = str + hex_chr.charAt((num >> (j * 8 + 4)) & 0x0F)
+ hex_chr.charAt((num >> (j * 8)) & 0x0F);
return str;
}
/*
* Convert a string to a sequence of 16-word blocks, stored as an array.
* Append padding bits and the length, as described in the MD5 standard.
*/
private int[] str2blks_MD5(String str) {
int nblk = ((str.length() + 8) >> 6) + 1;
int[] blks = new int[nblk * 16];
int i = 0;
for (i = 0; i < nblk * 16; i++) {
blks[i] = 0;
}
for (i = 0; i < str.length(); i++) {
blks[i >> 2] |= str.charAt(i) << ((i % 4) * 8);
}
blks[i >> 2] |= 0x80 << ((i % 4) * 8);
blks[nblk * 16 - 2] = str.length() * 8;
return blks;
}
/*
* Add integers, wrapping at 2^32
*/
private int add(int x, int y) {
return ((x & 0x7FFFFFFF) + (y & 0x7FFFFFFF)) ^ (x & 0x80000000)
^ (y & 0x80000000);
}
/*
* Bitwise rotate a 32-bit number to the left
*/
private int rol(int num, int cnt) {
return (num << cnt) | (num >>> (32 - cnt));
}
/*
* These functions implement the basic operation for each round of the
* algorithm.
*/
private int cmn(int q, int a, int b, int x, int s, int t) {
return add(rol(add(add(a, q), add(x, t)), s), b);
}
private int ff(int a, int b, int c, int d, int x, int s, int t) {
return cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
private int gg(int a, int b, int c, int d, int x, int s, int t) {
return cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
private int hh(int a, int b, int c, int d, int x, int s, int t) {
return cmn(b ^ c ^ d, a, b, x, s, t);
}
private int ii(int a, int b, int c, int d, int x, int s, int t) {
return cmn(c ^ (b | (~d)), a, b, x, s, t);
}
/*
* Take a string and return the hex representation of its MD5.
*/
public String calcMD5(String str) {
int[] x = str2blks_MD5(str);
int a = 0x67452301;
int b = 0xEFCDAB89;
int c = 0x98BADCFE;
int d = 0x10325476;
for (int i = 0; i < x.length; i += 16) {
int olda = a;
int oldb = b;
int oldc = c;
int oldd = d;
a = ff(a, b, c, d, x[i + 0], 7, 0xD76AA478);
d = ff(d, a, b, c, x[i + 1], 12, 0xE8C7B756);
c = ff(c, d, a, b, x[i + 2], 17, 0x242070DB);
b = ff(b, c, d, a, x[i + 3], 22, 0xC1BDCEEE);
a = ff(a, b, c, d, x[i + 4], 7, 0xF57C0FAF);
d = ff(d, a, b, c, x[i + 5], 12, 0x4787C62A);
c = ff(c, d, a, b, x[i + 6], 17, 0xA8304613);
b = ff(b, c, d, a, x[i + 7], 22, 0xFD469501);
a = ff(a, b, c, d, x[i + 8], 7, 0x698098D8);
d = ff(d, a, b, c, x[i + 9], 12, 0x8B44F7AF);
c = ff(c, d, a, b, x[i + 10], 17, 0xFFFF5BB1);
b = ff(b, c, d, a, x[i + 11], 22, 0x895CD7BE);
a = ff(a, b, c, d, x[i + 12], 7, 0x6B901122);
d = ff(d, a, b, c, x[i + 13], 12, 0xFD987193);
c = ff(c, d, a, b, x[i + 14], 17, 0xA679438E);
b = ff(b, c, d, a, x[i + 15], 22, 0x49B40821);
a = gg(a, b, c, d, x[i + 1], 5, 0xF61E2562);
d = gg(d, a, b, c, x[i + 6], 9, 0xC040B340);
c = gg(c, d, a, b, x[i + 11], 14, 0x265E5A51);
b = gg(b, c, d, a, x[i + 0], 20, 0xE9B6C7AA);
a = gg(a, b, c, d, x[i + 5], 5, 0xD62F105D);
d = gg(d, a, b, c, x[i + 10], 9, 0x02441453);
c = gg(c, d, a, b, x[i + 15], 14, 0xD8A1E681);
b = gg(b, c, d, a, x[i + 4], 20, 0xE7D3FBC8);
a = gg(a, b, c, d, x[i + 9], 5, 0x21E1CDE6);
d = gg(d, a, b, c, x[i + 14], 9, 0xC33707D6);
c = gg(c, d, a, b, x[i + 3], 14, 0xF4D50D87);
b = gg(b, c, d, a, x[i + 8], 20, 0x455A14ED);
a = gg(a, b, c, d, x[i + 13], 5, 0xA9E3E905);
d = gg(d, a, b, c, x[i + 2], 9, 0xFCEFA3F8);
c = gg(c, d, a, b, x[i + 7], 14, 0x676F02D9);
b = gg(b, c, d, a, x[i + 12], 20, 0x8D2A4C8A);
a = hh(a, b, c, d, x[i + 5], 4, 0xFFFA3942);
d = hh(d, a, b, c, x[i + 8], 11, 0x8771F681);
c = hh(c, d, a, b, x[i + 11], 16, 0x6D9D6122);
b = hh(b, c, d, a, x[i + 14], 23, 0xFDE5380C);
a = hh(a, b, c, d, x[i + 1], 4, 0xA4BEEA44);
d = hh(d, a, b, c, x[i + 4], 11, 0x4BDECFA9);
c = hh(c, d, a, b, x[i + 7], 16, 0xF6BB4B60);
b = hh(b, c, d, a, x[i + 10], 23, 0xBEBFBC70);
a = hh(a, b, c, d, x[i + 13], 4, 0x289B7EC6);
d = hh(d, a, b, c, x[i + 0], 11, 0xEAA127FA);
c = hh(c, d, a, b, x[i + 3], 16, 0xD4EF3085);
b = hh(b, c, d, a, x[i + 6], 23, 0x04881D05);
a = hh(a, b, c, d, x[i + 9], 4, 0xD9D4D039);
d = hh(d, a, b, c, x[i + 12], 11, 0xE6DB99E5);
c = hh(c, d, a, b, x[i + 15], 16, 0x1FA27CF8);
b = hh(b, c, d, a, x[i + 2], 23, 0xC4AC5665);
a = ii(a, b, c, d, x[i + 0], 6, 0xF4292244);
d = ii(d, a, b, c, x[i + 7], 10, 0x432AFF97);
c = ii(c, d, a, b, x[i + 14], 15, 0xAB9423A7);
b = ii(b, c, d, a, x[i + 5], 21, 0xFC93A039);
a = ii(a, b, c, d, x[i + 12], 6, 0x655B59C3);
d = ii(d, a, b, c, x[i + 3], 10, 0x8F0CCC92);
c = ii(c, d, a, b, x[i + 10], 15, 0xFFEFF47D);
b = ii(b, c, d, a, x[i + 1], 21, 0x85845DD1);
a = ii(a, b, c, d, x[i + 8], 6, 0x6FA87E4F);
d = ii(d, a, b, c, x[i + 15], 10, 0xFE2CE6E0);
c = ii(c, d, a, b, x[i + 6], 15, 0xA3014314);
b = ii(b, c, d, a, x[i + 13], 21, 0x4E0811A1);
a = ii(a, b, c, d, x[i + 4], 6, 0xF7537E82);
d = ii(d, a, b, c, x[i + 11], 10, 0xBD3AF235);
c = ii(c, d, a, b, x[i + 2], 15, 0x2AD7D2BB);
b = ii(b, c, d, a, x[i + 9], 21, 0xEB86D391);
a = add(a, olda);
b = add(b, oldb);
c = add(c, oldc);
d = add(d, oldd);
}
return rhex(a) + rhex(b) + rhex(c) + rhex(d);
}
}
使用方法：
MD5 md5=MD5.getInstance();
md5.calcMD5("cj");
System.out.println(" md5(cj,32) = "+md5.calcMD5("cj")); // 结果是 md5(cj,32) = 28198b369067e88dab9fefe85484dbf4
方法二：
public class MD5 {
private String inStr;
private MessageDigest md5;
/* 下面是构造函数 */
public MD5(String inStr) {
this.inStr = inStr;
try {
this.md5 = MessageDigest.getInstance("MD5");
} catch (Exception e) {
System.out.println(e.toString());
e.printStackTrace();
}
}
/* 下面是关键的md5算法 */
public String compute() {
char[] charArray = this.inStr.toCharArray();
byte[] byteArray = new byte[charArray.length];
for (int i = 0; i < charArray.length; i++)
byteArray[i] = (byte) charArray[i];
byte[] md5Bytes = this.md5.digest(byteArray);
StringBuffer hexValue = new StringBuffer();
for (int i = 0; i < md5Bytes.length; i++) {
int val = ((int) md5Bytes[i]) & 0xff;
if (val < 16)
hexValue.append("0");
hexValue.append(Integer.toHexString(val));
}
return hexValue.toString();
}
}
使用方法：
MD5 md5=new MD5("cj");
System.out.println(" md5(cj,32) = "+md5.compute()); // 结果是 md5(cj,32) = 28198b369067e88dab9fefe85484dbf4