How to Compute an Array’s Average in Java and Groovy: For‑Loop vs Lambda

Average with Java for‑loop

Define an int array, iterate with a classic for loop, accumulate the sum, then compute the average as a double by multiplying the sum by 1.0 and dividing by the array length. Example code:

package com.fun.ztest.java;

import com.fun.frame.SourceCode;

public class Tdd extends SourceCode {
    public static void main(String[] args) {
        int[] array = {43, 54, 6, 2, 75, 34, 1};
        int sum = 0;
        for (int i = 0; i < array.length; i++) {
            sum += array[i];
        }
        output(sum * 1.0 / array.length);
    }
}

The program prints 30.714285714285715, the arithmetic mean of the elements.

Average with Java Stream API (Lambda)

Convert the primitive int[] to a List<Integer> using ArrayUtils.toObject (Apache Commons Lang 3). Then use stream() with Collectors.summingInt to obtain the sum, and compute the average in the same way as the loop version.

package com.fun.ztest.java;

import com.fun.frame.SourceCode;
import org.apache.commons.lang3.ArrayUtils;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Tdd extends SourceCode {
    public static void main(String[] args) {
        int[] array = {43, 54, 6, 2, 75, 34, 1};
        List<Integer> integers = Arrays.asList(ArrayUtils.toObject(array));
        Integer sum = integers.stream()
                              .collect(Collectors.summingInt(x -> x));
        output(sum * 1.0 / array.length);
    }
}

The output is identical: 30.714285714285715.

Average with Groovy

Groovy provides collection helpers that eliminate boilerplate. Define the numbers as a Groovy list, then call sum() and divide by size(). No explicit conversion or loop is required.

package com.fun.ztest.groovy;

import com.fun.frame.httpclient.FanLibrary;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class Td extends FanLibrary {
    private static Logger logger = LoggerFactory.getLogger(Td.class);

    public static void main(String[] args) {
        def array = [43, 54, 6, 2, 75, 34, 1];
        output(array.sum() / array.size());
    }
}

Running the Groovy script prints 30.7142857143, demonstrating the same result with considerably less code.