Java实现MD5加密

diaolanshan

[size=medium]import java.security.MessageDigest;
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 & 0x000000FF) / 16;
     lsb = ((int)b & 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));
}
}
[size=medium]如上代码为java语言实现md5加密算法，输出为加密后的密文！
通常将加密后的密文保存在数据库中，如果需要比较只比较他们的用md5加密过后的密文。
同时，md5加密算法是不可逆的，破解的难度很高，虽然有人破解了md5,但是他们所用的硬件环境不是我们普通的计算机所比拟的，山大的一位很牛的女教授也破解了md5,不过不怎么了解