生成随机字符串 工具类

package com.shop.cyshop.commons.utils;

import java.util.Date;
import java.util.Random;
import java.util.UUID;

/**
 * @Name RandomStringUtil
 * @Descr 生成随机字符串
 * @author lnexin@aliyun.com
 * @date 2015年10月15日下午2:36:05
 */
public class RandomStringUtil {
    /**
     * @param passLength
     *            : 要生成多少长度的字符串
     * @param type
     *            : 需要哪种类型
     * @return 根据传入的type来判定
     */
    
    // 可以根据自己需求来删减下面的代码，不要要的类型可以删掉
     
    // type=0：纯数字(0-9)
    // type=1：全小写字母(a-z)
    // type=2：全大写字母(A-Z)
    // type=3: 数字+小写字母
    // type=4: 数字+大写字母
    // type=5：大写字母+小写字母
    // type=6：数字+大写字母+小写字母
    // type=7：固定长度33位：根据UUID拿到的随机字符串，去掉了四个"-"(相当于长度33位的小写字母加数字)

    public static String getRandomCode(int passLength, int type) {
        StringBuffer buffer = null;
        StringBuffer sb = new StringBuffer();
        Random r = new Random();
        r.setSeed(new Date().getTime());
        switch (type) {
        case 0:
            buffer = new StringBuffer("123456789");
            break;
        case 1:
            buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyz");
            break;
        case 2:
            buffer = new StringBuffer("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
            break;
        case 3:
            buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyz");
            break;
        case 4:
            buffer = new StringBuffer("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ");
            break;
        case 5:
            buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
            break;
        case 6:
            buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");
            sb.append(buffer.charAt(r.nextInt(buffer.length() - 10)));
            passLength -= 1;
            break;
        case 7:
            String s = UUID.randomUUID().toString();
            sb.append(s.substring(0, 8) + s.substring(9, 13) + s.substring(14, 18) + s.substring(19, 23) + s.substring(24));
        }

        if (type != 7) {
            int range = buffer.length();
            for (int i = 0; i < passLength; ++i) {
                sb.append(buffer.charAt(r.nextInt(range)));
            }
        }
        return sb.toString();
    }


    public static String getRandom() {
        String num = "";
        for (int i = 0; i < 4; i++) {
            num = num + String.valueOf((int) Math.floor(Math.random() * 9 + 1));
        }
        return num;
    }
}