java 实现MD5加密算法的简单实例

import java.security.NoSuchAlgorithmException;  
 
public class MD5HashUtil  
{  
private MessageDigest md = null;  
private static MD5HashUtil md5 = null;  
private static final char[] hexChars ={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};  
 
  /** 
  * Constructor is private so you must use the getInstance method 
  */  
  private MD5HashUtil() throws NoSuchAlgorithmException  
  {  
   md = MessageDigest.getInstance("MD5");  
  }  
  /** 
  * This returns the singleton instance 
  */  
 public static MD5HashUtil getInstance()throws NoSuchAlgorithmException  
  {  
    if (md5 == null)  
    {  
     md5 = new MD5HashUtil();  
   }  
   return (md5);  
  }  
 public static String hashCode(String dataToHash) throws NoSuchAlgorithmException{  
 return getInstance().hashData(dataToHash.getBytes());  
 }  
 public static String hashCode(byte[] dataToHash) throws NoSuchAlgorithmException{  
 return getInstance().hashData(dataToHash);  
 }  
public String hashData(byte[] dataToHash) {  
   return hexStringFromBytes((calculateHash(dataToHash))).toLowerCase();  
}  
private byte[] calculateHash(byte[] dataToHash)  
{  
   md.update(dataToHash, 0, dataToHash.length);  
   return (md.digest());  
 }  
public String hexStringFromBytes(byte[] b)  
{  
  String hex = "";  
  int msb;  
  int lsb = 0;  
  int i;  
  // MSB maps to idx 0  
  for (i = 0; i < b.length; i++)  
  {  
   msb = ((int)b[i] & 0x000000FF) / 16;  
   lsb = ((int)b[i] & 0x000000FF) % 16;  
    hex = hex + hexChars[msb] + hexChars[lsb];  
   }  
   return(hex);  
  }  
 
public static void main(String args[]) throws NoSuchAlgorithmException  
{  
String string = "my name is zhangli";  
System.out.println(string);  
System.out.println(hashCode(string));  
}  
}