生成指定长度随机数工具类

package com.tefei.isak.common;

import java.util.Random;

/**
 * @author linyh
 * @email 1503386669@qq.com
 * @date 2020/8/17 9:13
 * 生成随机数
 */
public class RandomUtils {
    /**
     * 字符混合数字数组(长度为62)
     */
    private static final String[] charAndNumber = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "A", "b", "B", "c", "C", "d", "D"
            , "e", "E", "f", "F", "g", "G", "h", "H", "i", "I", "j", "J", "k", "K", "l", "L", "m", "M"
            , "n", "N", "o", "O", "p", "P", "q", "Q", "r", "R", "s", "S", "t", "T", "u", "U", "v", "V"
            , "w", "W", "x", "X", "y", "Y", "z", "Z"};
    /**
     * 纯数字数组(长度为10)
     */
    private static final String[] onlyNumber = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
    /**
     * 纯字符数组(长度为52)
     */
    private static final String[] onlyChar = {"a", "A", "b", "B", "c", "C", "d", "D", "e", "E", "f", "F", "g", "G", "h", "H", "i", "I", "j"
            , "J", "k", "K", "l", "L", "m", "M", "n", "N", "o", "O", "p", "P", "q", "Q", "r", "R", "s"
            , "S", "t", "T", "u", "U", "v", "V", "w", "W", "x", "X", "y", "Y", "z", "Z"};

    /**
     * 随机生成长度为length的字符串(字符混合数字)
     *
     * @param length
     * @return
     */
    public static StringBuffer generateCharAndNumber(int length) {
        StringBuffer stringBuffer = new StringBuffer();
        Random random = new Random();
        for (int i = 1; i <= length; ++i) {
            stringBuffer.append(charAndNumber[random.nextInt(62)]);
        }
        return stringBuffer;
    }

    /**
     * 随机生成长度为length的字符串(只包含字符)
     * @param length
     * @return
     */
    public static StringBuffer generateChar(int length) {
        StringBuffer stringBuffer = new StringBuffer();
        Random random = new Random();
        for (int i = 1; i <= length; ++i) {
            stringBuffer.append(onlyChar[random.nextInt(52)]);
        }
        return stringBuffer;
    }

    /**
     * 随机生成长度为length的字符串(只包含数字)
     * @param length
     * @return
     */
    public static StringBuffer generateNumber(int length) {
        StringBuffer stringBuffer = new StringBuffer();
        Random random = new Random();
        for (int i = 1; i <= length; ++i) {
            stringBuffer.append(onlyNumber[random.nextInt(10)]);
        }
        return stringBuffer;
    }
}