import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;public class GetMd5 {  public static void main(String[] args) {    String a="123";  System.out.println(getMd5(a));  }  /**   * 獲取文本字段的MD5值   * @param txt   * @return   */  public static String getMd5(String txt){    String rs = "";    String[] hexDigits = { "0", "1", "2", "3", "4", "5", "6", "7", "8","9", "a", "b", "c", "d", "e", "f" };    try {      MessageDigest messageDigest = MessageDigest.getInstance("MD5");      byte[] b = messageDigest.digest(txt.getBytes());      StringBuffer resultSb = new StringBuffer();      for (int i = 0; i < b.length; i++) {        int n = b[i];        if (n < 0)          n = 256 + n;        int d1 = n / 16;        int d2 = n % 16;        resultSb.append(hexDigits[d1] + hexDigits[d2]);      }      rs = resultSb.toString();    } catch (NoSuchAlgorithmException e) {      e.printStackTrace();    }    return rs;  }}