使用MessageDigest类实现MD5加密
使用java.security.MessageDigest类来实现MD5、SHA加密，代码如下：
import java.security.MessageDigest;public class MD5AndSHA {public final static String MD5_SHA(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(); //如果输入“SHA”，就是实现SHA加密。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(MD5AndSHA.MD5_SHA("123456"));}}