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);
}