CR.ComputeMean

Test1.java

import java.math.BigDecimal;
import java.util.*;

public class Test1 {
    
    private static double computeMean1(double... values) {
        double sum = 0.0;
        for (double x : values) {
            sum += x;
        }
        return sum / values.length;
    }

    private static double computeMean2(double... values) {
        double sum = 0.0;
        for (double x : values) {
            sum += x / values.length;
        }
        return sum;
    }

    private static double computeMean3(double... values) {
        double sum = 0.0;
        double f = 1.0 / values.length;
        for (double x : values) {
            sum += x * f;
        }
        return sum;
    }
    
    private static int dcmp(double a, double b) {
        a = Math.abs(a);
        b = Math.abs(b);
        
        return Double.compare(a, b);
    }
    
    private static double computeMean4(Double... values) {
        Arrays.sort(values, (a, b) -> dcmp(a, b));
        double sum = 0.0;
        
        for (double d : values) {
            sum += d;
        }
        
        return sum / values.length;
    }
    
    private static BigDecimal computeMeanBD(BigDecimal... values) {
        BigDecimal sum = BigDecimal.ZERO;
        
        for (BigDecimal bd : values) {
            sum = sum.add(bd);
        }
        
        return sum.divide(BigDecimal.valueOf(values.length));
    }

    public static void main(String[] args) {
        double[] values1 = { 10E9, 0.001, 0.001, 0.001 };
        System.out.println(computeMean1(values1));
        System.out.println(computeMean2(values1));
        System.out.println(computeMean3(values1));
        
        Double[] values2 = { 10E9, 0.001, 0.001, 0.001 };
        System.out.println(computeMean4(values2));
        
        BigDecimal[] values3 = { BigDecimal.valueOf(10E9), 
                                 BigDecimal.valueOf(0.001), 
                                 BigDecimal.valueOf(0.001), 
                                 BigDecimal.valueOf(0.001) };
        
        System.out.println(computeMeanBD(values3));
    }
}

Test2.java

public class Test2 {

    public static void main(String[] args) {
        double[] values = new double[1_000_000];
        
        values[0] = 1e9;
        
        for (int i = 1; i < values.length; ++i) {
            values[i] = 1e-6;
        }
        
        printSum(values);
        
        reverse(values);
        
        printSum(values);
    }
    
    private static void printSum(double[] values) {
        double sum = 0.0;
        
        for (double d : values) {
            sum += d;
        }
        
        System.out.println(sum);
    }
    
    private static void reverse(double[] values) {
        for (int lo = 0, hi = values.length - 1; lo < hi; ++lo, --hi) {
            double tmp = values[lo];
            values[lo] = values[hi];
            values[hi] = tmp;
        }
    }
}

Hi, you can use Arrays.sort(values, Test1::dcmp); and return sum.divide(BigDecimal.valueOf(values.length), MathContext.DECIMAL128);.

And here's a reference type typo: computeMean4(Double... values).

Sorry, no, that's correct.