计算一个字符串的MD5

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 使用方式:String test_md5 = MD5.MD5("test");
 * @author shuaicenglou
 *
 */
public class MD5 {
	 
	public static String MD5(String sourceStr) {
	    String result = "";
	    try {
	      MessageDigest md = MessageDigest.getInstance("MD5");
	      md.update(sourceStr.getBytes());
	      byte b[] = md.digest();
	      int i;
	      StringBuffer buf = new StringBuffer("");
	      for (int offset = 0; offset < b.length; offset++) {
	        i = b[offset];
	        if (i < 0)
	          i += 256;
	        if (i < 16)
	          buf.append("0");
	        buf.append(Integer.toHexString(i));
	      }
	      result = buf.toString().substring(8, 24);
	    } catch (NoSuchAlgorithmException e) {
	      System.out.println(e);
	    }
	    return result;
	  }
	}