生成隨機字符串

1） 生成主鍵隨機數： 時間+隨機數

// package com.demo.utils;

import java.util.Random;

/**
 * 生成主鍵隨機數
 * 時間+++ 隨機數
 * Created by hll on 2018/5/31.
 */
public class KeyUtil {


    /**
     * 生成唯一的主鍵
     * 格式: 時間+隨機數
     * @return
     */
    public static synchronized String getKey() {
        Random random = new Random();
        Integer number = random.nextInt(900000) + 100000;//生成6位隨機數

        return System.currentTimeMillis() + String.valueOf(number);
    }
public  static  void main(String[] args){
    System.out.println(getKey());
	}
}

2）隨機字符/數工具類

package cn.uctimes.product.library.commons.utils;

/**
 * 隨機字符/數工具類
 * 
 * @author hezhuangzhuang
 * @date 2018-01-07 16:18:02
 *
 */
public class RandomUtil {
	private static class RandomUtilHandler {
		private static RandomUtil instance = new RandomUtil();
	}

	private RandomUtil() {
	}

	public static RandomUtil getInstance() {
		return RandomUtilHandler.instance;
	}

	/**
	 * 生成小寫大寫數字混合的固定長度的隨機字符串
	 * @param length
	 * @return
	 */
	public String genMixString(int length) {
		return genString(length,null);
	}
	
	/**
	 * 生成隨機字符串
	 * @param length
	 * @param type 0:只生成大寫字母,1只生成小寫字母,2:只生成數字,其他/null:混合類型
	 * @return
	 */
	public String genString(Integer length,Integer type){
		if(null == length)
			throw new RuntimeException("length can not be null");
		char[] ss = new char[length];
		int i = 0;
		Integer f = type;
		while (i < length) {
			if(null == type )
				f = (int) (Math.random() * 3);
			if (f == 0)
				ss[i] = (char) ('A' + Math.random() * 26);
			else if (f == 1)
				ss[i] = (char) ('a' + Math.random() * 26);
			else if (f == 2)
				ss[i] = (char) ('0' + Math.random() * 10);
			else{
				type = null;
				continue;
			}
				
			i++;
		}
		String is = new String(ss);
		return is;
	}
	
	public static void main(String[] args) {
	System.out.println(RandomUtil.getInstance().genString(10, 0));
	}
}