先正常算出SHA1的值（普通是以16进制串表示），将这个16进制串在内存中以字节流保存，然后Base64计算的结果不知道是不是就是Sha1-Digest的值。
经编程测试，确实如此。
给你个MD5的加密算法package test
import java.security.MessageDigest
/**
* <p>Title: </p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2003</p>
* <p>Company: </p>
* @author unascribed
* @version 1.0
*/
public class StringUtil {
private final static String[] hexDigits = {
"0", "1", "2", "3", "4", "5", "6", "7",
"8", "9", "a", "b", "c", "d", "e", "f"}
/**
* 转换字节数组为16进制字串
* @param b 字节数组
* @return 16进制字串
*/
public static String byteArrayToHexString(byte[] b) {
StringBuffer resultSb = new StringBuffer()
for (int i = 0i <b.lengthi++) {
resultSb.append(byteToHexString(b[i]))
}
return resultSb.toString()
}
private static String byteToHexString(byte b) {
int n = b
if (n <0)
n = 256 + n
int d1 = n / 16
int d2 = n % 16
return hexDigits[d1] + hexDigits[d2]
}
public static String MD5Encode(String origin) {
String resultString = null
try {
resultString=new String(origin)
MessageDigest md = MessageDigest.getInstance("MD5")
resultString=byteArrayToHexString(md.digest(resultString.getBytes()))
}
catch (Exception ex) {
}
return resultString
}
public static void main(String[] args){
System.err.println(MD5Encode("a"))
}
}
在RFC 1321中，给出了Test suite用来检验你的实现是否正确：
MD5 ("") = d41d8cd98f00b204e9800998ecf8427e
MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661
MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72
MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0
MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b
