代码如下: package com.test.j2se; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class MD5 { /**数据加密 * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub try { MessageDigest code = MessageDigest.getInstance("MD5"); String str = "ADFSE"; System.out.println("before md5:"+str); code.update(str.getBytes()); byte[] bs = code.digest(); StringBuffer sb = new StringBuffer(); for(int i =0;i<bs.length;i++) { // System.out.println("bs["+i+"]="+bs[i]); int v = bs[i]& 0xff; if(v <16) { sb.append(0); } sb.append(Integer.toHexString(v).toUpperCase()); } System.out.println("length ="+sb.length()); System.out.println("after md5 :"+sb.toString()); System.out.println("5tohexStrin="+Integer.toHexString(17)); } catch (NoSuchAlgorithmException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } 一般验证码:我们可以对其进行加密,然后将输入的验证码加密后跟其对比。。