Java实现的MD5加密类

import java.security.*;     
   
public class MD5{     
   
 public final static String getMD5(String s){     
  char hexDigits[] = {     
    '0', '1', '2', '3',     
    '4', '5', '6', '7',     
    '8', '9', 'a', 'b',     
    'c', 'd', 'e', 'f'};     
  try {     
   byte[] strTemp = s.getBytes();     
   MessageDigest mdTemp = MessageDigest.getInstance("MD5");     
   mdTemp.update(strTemp);     
   byte[] md = mdTemp.digest();     
   int j = md.length;     
   char str[] = new char[j * 2];     
   int k = 0;     
   for (int i = 0; i < j; i++) {     
    byte byte0 = md[i];     
    str[k++] = hexDigits[byte0 >>> 4 & 0xf];     
    str[k++] = hexDigits[byte0 & 0xf];     
   }     
   return new String(str);     
  }catch (Exception e){     
   return null;     
  }     
 }     
     
 public static void main(String[] args){     
   
  System.out.print(MD5.getMD5("abcd"));     
 }    
}