Finding the max/min value in an array of primitives using Java

Question

Using Commons Lang (to convert) + Collections (to min/max)

import java.util.Arrays;
import java.util.Collections;

import org.apache.commons.lang.ArrayUtils;

public class MinMaxValue {

    public static void main(String[] args) {
        char[] a = {'3', '5', '1', '4', '2'};

        List b = Arrays.asList(ArrayUtils.toObject(a));

        System.out.println(Collections.min(b));
        System.out.println(Collections.max(b));
   }
}

Note that Arrays.asList() wraps the underlying array, so it should not be too memory intensive and it should not perform a copy on the elements of the array.

You can simply use the new Java 8 Streams but you have to work with int.

The stream method of the utility class Arrays gives you an IntStream on which you can use the min method. You can also do max, sum, average,...

The getAsInt method is used to get the value from the OptionalInt

import java.util.Arrays;

public class Test {
    public static void main(String[] args){
        int[] tab = {12, 1, 21, 8};
        int min = Arrays.stream(tab).min().getAsInt();
        int max = Arrays.stream(tab).max().getAsInt();
        System.out.println("Min = " + min);
        System.out.println("Max = " + max)
    }

}

==UPDATE==

If execution time is important and you want to go through the data only once you can use the summaryStatistics() method like this

import java.util.Arrays;
import java.util.IntSummaryStatistics;

public class SOTest {
    public static void main(String[] args){
        int[] tab = {12, 1, 21, 8};
        IntSummaryStatistics stat = Arrays.stream(tab).summaryStatistics();
        int min = stat.getMin();
        int max = stat.getMax();
        System.out.println("Min = " + min);
        System.out.println("Max = " + max);
    }
}

This approach can give better performance than classical loop because the summaryStatistics method is a reduction operation and it allows parallelization.

The Google Guava library has min and max methods in its Chars, Ints, Longs, etc. classes.

So you can simply use:

Chars.min(myarray)

No conversions are required and presumably it's efficiently implemented.

Yes, it's done in the Collections class. Note that you will need to convert your primitive char array to a Character[] manually.

A short demo:

import java.util.*;

public class Main {

    public static Character[] convert(char[] chars) {
        Character[] copy = new Character[chars.length];
        for(int i = 0; i < copy.length; i++) {
            copy[i] = Character.valueOf(chars[i]);
        }
        return copy;
    }

    public static void main(String[] args) {
        char[] a = {'3', '5', '1', '4', '2'};
        Character[] b = convert(a);
        System.out.println(Collections.max(Arrays.asList(b)));
    }
}