java - 程序每次应该随机时都会给出相同的结果

Question

该程序的目标是取 2 个随机变量作为分数，看看它们是否已经在缩减项中。假设的概率是 6/(pi^2)。我运行了 1,000 种不同的变量组合，并确定有多少已经减少和尚未减少。然后我求解 pi。

但是每次我运行它时，输出都会给我“pi is 2.449489742783178”。

有谁知道为什么？谢谢。

import java.util.*;

public class ratio1 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int nonReducedCount = 0; //counts how many non reduced ratios there are
        for(int i =1; i<=1000; i++){

            Random rand = new Random();
            int n = rand.nextInt(1000)+1;  //random int creation
            int m = rand.nextInt(1000)+1;
            //Ratio ratio = new Ratio(n,m);
            if (gcd(n,m)> 1 ){ // if the ratio was not already fully reduced
                nonReducedCount++; // increase the count of non reduced ratios
            }   
        }

        int reducedCount = 1000 - nonReducedCount; //number of times the ratio was reduced already
        double reducedRatio = reducedCount / nonReducedCount; //the ratio for reduced and not reduced
        reducedRatio *= 6;
        reducedRatio = Math.sqrt(reducedRatio);
        System.out.println("pi is " + reducedRatio);
    }

    public static int gcd(int a, int b) { return b==0 ? a : gcd(b,a%b); }

}

Answer 1

When you divide two integers, you get integer division, with an integer result, even if you later assign the result to a double. Try

double reducedRatio = (double)reducedCount / nonReducedCount;

i.e. convert one of the operands to a double.