随机数工具类

import java.util.Random;

public class RandomUtil {
    private static final String BASE_NUMBER = "0123456789";
    private static final String BASE_CHAR = "abcdefghijklmnopqrstuvwxyz";
    private static final String BASE_CHAR_NUMBER = "abcdefghijklmnopqrstuvwxyz0123456789";

    private RandomUtil() {
    }

    /**
     * 获取范围内的随机数字
     * @param min 最小值
     * @param max 最大值
     * @return
     */
    public static int randomInt(int min, int max) {
        Random random = new Random();
        return random.nextInt(max - min) + min;
    }

    /**
     * 获取大写的随机字符串
     * @param length 长度
     * @return
     */
    public static String randomUcString(int length) {
        return randomString(BASE_CHAR_NUMBER, length).toUpperCase();
    }

    /**
     * 获取小写的随机字符串
     * @param length 长度
     * @return
     */
    public static String randomLcString(int length){
        return randomString(BASE_CHAR_NUMBER, length);
    }

    /**
     * 获取随机数字字符串
     * @param length 长度
     * @return
     */
    public static String randomNumbers(int length) {
        return randomString(BASE_NUMBER, length);
    }

    /**
     * 获取随机字符串
     * @param baseString 字符串模板
     * @param length 长度
     * @return
     */
    public static String randomString(String baseString, int length) {
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        if (length < 1) {
            length = 1;
        }

        int baseLength = baseString.length();

        for(int i = 0; i < length; ++i) {
            int number = random.nextInt(baseLength);
            sb.append(baseString.charAt(number));
        }

        return sb.toString();
    }
}