本文实例讲述了Java实现MD5加密的方法。分享给大家供大家参考。具体实现方法如下：
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[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));
}
}
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
希望本文所述对大家的java程序设计有所帮助。
