Java hashmap choose random but by chance

Question

I have 2 hashmaps.

rewards<integer,integer>
chances<integer,integer>

rewards is like : 57,500000000;9210,2500;9209,50;6660,1;6 (id-count)

chances is like : 57,95;9210,70;9209,65;6660,15; (id-chance %) id is the same both maps.

So i want to choose one id but by these chances so low chances will have lower chance to be selected. i am fully confused. thanks you! (but i need to chooce 1 id , not zero not more than 1)

i just want to select an id from rewards , but with chances not all to be the same chance.. for example 57 id has chance 95% , 9210 id has chance 70% — user3697574, Feb 25 '15 at 04:29
Sum the total chance percentages, generate a random number lower than it, then map that number back to an index. — Adrian Leonhard, Feb 25 '15 at 04:43

score 0 · Answer 1 · edited May 23 '17 at 12:20

This explains it in more detail.

int sumOfPercentages = ...; //ex) 100
Random ran = new Random();
int ranNumber = ran.nextInt(sumOfPercentages);

Integer id = -1;
int current = 0;
for (Map.Entry<Integer, Integer> entry : chances.entrySet())
{
    current += entry.getValue();
    if(ranNumber < current)
    {
      id = entry.getKey();
      break;
    }
}

System.out.println(rewards.get(id));

Java hashmap choose random but by chance

1 Answers1