java 生成一定长度的数目字或字符串，交易码

package com.fjxhx.wxpay.util;

import java.util.Random;

/**
 * User: rizenguo
 * Date: 2014/10/29
 * Time: 14:18
 */
public class RandomStringGenerator {

    /**
     * 获取一定长度的随机字符串
     * @param length 指定字符串长度
     * @return 一定长度的字符串
     */
    public static String getRandomStringByLength(int length) {
        String base = "abcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        return sb.toString();
    }
    
    public static String getRandomIntegerByLength(int length) {
    	String base = "0123456789";
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        return sb.toString();
    }
    public static void main(String[] args) {
		RandomStringGenerator a=new RandomStringGenerator();
		String b=a.getRandomStringByLength(13);
		System.out.println(b);
	}

}

交易码

package com.fjxhx.wxpay.util;


/**
 * 交易码生成器
 * @author wx
 *
 */
public class TradeNoGenerator {

	public static String generator(String tradeType) {
		StringBuffer tradeNo = new StringBuffer();
		tradeNo.append(tradeType);
		tradeNo.append(System.currentTimeMillis());
		tradeNo.append(RandomStringGenerator.getRandomIntegerByLength(6));
		return tradeNo.toString();
	}
	
	public static void main(String[] args) {
		System.out.println(TradeNoGenerator.generator("JSAPI"));
	}
}