SumOfFloatingNumbers.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
  OUTPUT:
  + Sum of 10000 double numbers
  For the 1st shuffling, sum = 4999499.9999999935
  For the 2nd shuffling, sum = 4999499.999999965
  
  + Sum of 10000 float numbers
  For the 1st shuffling, sum = 4999512.5
  For the 2nd shuffling, sum = 4999498.5
*/
public class SumOfFloatingNumbers {
  
  static void testSumOfDoubles(int n) {
    List<Double> x = new ArrayList<Double>(n);
    for (int i = 0; i < n; i++)
      x.add(0.1d * i);
    
    // First shuffling
    Collections.shuffle(x);
    double res1 = 0d;
    for (Double e: x) res1 += e;
    
    // Second shuffling
    Collections.shuffle(x);
    double res2 = 0d;
    for (Double e: x) res2 += e;

    System.out.println("+ Sum of " + n + " double numbers");
    System.out.println("For the 1st shuffling, sum = " + res1);
    System.out.println("For the 2nd shuffling, sum = " + res2);
  }

  static void testSumOfFloats(int n) {
    List<Float> x = new ArrayList<Float>(n);
    for (int i = 0; i < n; i++)
      x.add(0.1f * i);
    
    // First shuffling
    Collections.shuffle(x);
    float res1 = 0f;
    for (Float e: x) res1 += e;
    
    // Second shuffling
    Collections.shuffle(x);
    float res2 = 0f;
    for (Float e: x) res2 += e;
    
    System.out.println("\n+ Sum of " + n + " float numbers");
    System.out.println("For the 1st shuffling, sum = " + res1);
    System.out.println("For the 2nd shuffling, sum = " + res2);
  }
  
  public static void main(String[] args) throws Exception {
    testSumOfDoubles(10000);
    testSumOfFloats(10000);
  }
}