Java生成六位验证码(发短信验证)

public String getRandNum(int charCount) {

         String charValue = "";

         for (int i = 0; i < charCount; i++) {

             char c = (char) (randomInt(0, 10) + '0');

             charValue += String.valueOf(c);

         }

         return charValue;
    }
 public int randomInt(int from, int to) {
         Random r = new Random();
         return from + r.nextInt(to - from);
     }