import java.security.MessageDigest;/** * Md5 工具 */public class Md5Util {    private static MessageDigest md5 = null;    static {        try {            md5 = MessageDigest.getInstance("MD5");        } catch (Exception e) {            System.out.println(e.getMessage());        }    }    /**     * 用于获取一个String的md5值     * @param string     * @return     */    public static String getMd5(String str) {        byte[] bs = md5.digest(str.getBytes());        StringBuilder sb = new StringBuilder(40);        for(byte x:bs) {            if((x & 0xff)>>4 == 0) {                sb.append("0").append(Integer.toHexString(x & 0xff));            } else {                sb.append(Integer.toHexString(x & 0xff));            }        }        return sb.toString();    }    public static void main(String[] args) {        System.out.println(getMd5("hello world"));    }}