public class WxAlgorithm{

 /**
 * @param moneySum 输入总金额
 * @param redNum 输入红包数量
 */
 private static void wxAlgorithm(double moneySum, int redNum) {
 // 设置最小的金额
 double moneyMin = 0.01;
 Random random = new Random();
 //精确小数点2位
 NumberFormat formatter = new DecimalFormat("#.##");
 for (int i=1;i<redNum;i++)
 {
  //随机一个数，数值范围在最小值与余额之间
  String money = formatter.format(random.nextDouble() * (moneySum - moneyMin) + moneyMin);
  //数值转换
    moneySum = Double.valueOf(formatter.format(moneySum - Double.valueOf(money)));
 
  System.out.println("第"+i+"个红包：" + money + "元 ,余额：" + moneySum);
 }
 
 System.out.println("最后个红包：" + moneySum + "元 ,余额：" + (moneySum - moneySum));
 }
 
 public static void main(String[] args) {
 wxAlgorithm(10.26, 9);
 }
}

public static double [] getMoney(double money, int num){
  Random r = new Random();
  DecimalFormat format = new DecimalFormat(".##");
  
  double middle = Double.parseDouble(format.format(money/num));
  double [] dou = new double[num];
  double redMoney = 0;
  double nextMoney = money;
  double sum = 0;
  int index = 0;
  for(int i=num;i>0;i--){
   if(i == 1){
    dou[index] = nextMoney;
   }else{
    while(true){
     String str = format.format(r.nextDouble()*nextMoney);
     redMoney = Double.parseDouble(str);
     if(redMoney>0 && redMoney < middle){
      break;
     }
    }
    nextMoney = Double.parseDouble(format.format(nextMoney - redMoney));
    sum = sum + redMoney;
    dou[index] = redMoney;
    middle = Double.parseDouble(format.format(nextMoney/(i-1)));
    index++;
   }
  }
  return dou;
 }

package com.sunron.test;

import java.math.BigDecimal;

import org.junit.Test;

public class HongBao {
 @Test
 public void testHonbao(){
 hb(100, 9, 0.01);//金额，个数，最少值
 //zb();
 }
 void hb(double total,int num,double min){
 for(int i=1;i<num;i++){
 double safe_total=(total-(num-i)*min)/(num-i);
 double money=Math.random()*(safe_total-min)+min;
 BigDecimal money_bd=new BigDecimal(money);
 money=money_bd.setScale(2,BigDecimal.ROUND_HALF_UP).doubleValue(); 
 total=total-money;
 BigDecimal total_bd=new BigDecimal(total);
 total=total_bd.setScale(2,BigDecimal.ROUND_HALF_UP).doubleValue();
 System.out.println("第"+i+"个红包："+money+",余额为:"+total+"元");
 }
 System.out.println("第"+num+"个红包："+total+",余额为:0元");
 }
 
 void zb(){
   for(int a=0;a<=10000;a++){
   if(a % 1000== 0) 
   System.out.println (a);
   }
  
 }

}

public static void main(String[] args) {
  //红包数
  int number = 10;
  //红包总额
  float total = 100;
  float money;
  //最小红包
  double min = 1;
  double max;
  int i = 1;
  List math = new ArrayList();
  DecimalFormat df = new DecimalFormat("###.##");
  while (i < number) {
   //保证即使一个红包是最大的了,后面剩下的红包,每个红包也不会小于最小值
   max = total - min * (number - i);
   int k = (int)(number - i) / 2;
   //保证最后两个人拿的红包不超出剩余红包
   if (number - i <= 2) {
    k = number - i;
   }
   //最大的红包限定的平均线上下
   max = max / k;
   //保证每个红包大于最小值,又不会大于最大值
   money = (int) (min * 100 + Math.random() * (max * 100 - min * 100 + 1));
   money = (float)money / 100;
   //保留两位小数
   money = Float.parseFloat(df.format(money));
   total=(int)(total*100 - money*100);
   total = total/100;
   math.add(money);
   System.out.println("第" + i + "个人拿到" + money + "剩下" + total);
   i++;
   //最后一个人拿走剩下的红包
   if (i == number) {
    math.add(total);
    System.out.println("第" + i + "个人拿到" + total + "剩下0");
   }
  }
//取数组中最大的一个值的索引
  System.out.println("本轮发红包中第" + (math.indexOf(Collections.max(math)) + 1) + "个人手气最佳");
 }