Finding minimum and maximum in Java 2D array

Question

I have been trying to figure this out for a while and need some help. I need to find the min/max values and print them out for a multidimensional array. Here are the two ways that I have tried.

import java.util.*;

class MinMax {
    public static void main(String[] args) {
        int[][] data = {{3, 2, 5},
                {1, 4, 4, 8, 13},
                {9, 1, 0, 2},
                {0, 2, 6, 3, -1, -8}};
        Arrays.sort(data);
        System.out.println("Minimum = " + data[0]);
        System.out.println("Maximum = " + data[data.length - 1]);
    }
}

This version complies but doesn't run.

import java.util.*;

class MinMax {
    public static void main(String[] args) {
        int[][] data = {{3, 2, 5},
                {1, 4, 4, 8, 13},
                {9, 1, 0, 2},
                {0, 2, 6, 3, -1, -8}};

    public static int getMaxValue(int[] numbers) {
        int maxValue = numbers[0];
        for (int i = 1; i < numbers.length; i++) {
            if (numbers[i] > maxValue) {
                maxValue = numbers[i];
            }
            return maxValue;
            {
                public static int getMinValue (int[] numbers) {
                    int minValue = numbers[0];
                    for (int i = 1; i < numbers.length; i++) {
                        if (numbers[i] < minValue) {
                            minValue = numbers[i];
                        }
                    }
                return minValue;
            }

This version just throws me a bunch of errors in compiling. Any help is greatly appreciated.

Solution 1

Ok, I've kinda fixed your code. Actually your mistake was that you have not been traversing all the cells of your multidimensional array.

So, I've added additional loop into getMinValue/getMinValue methods and fixed array elements addressing.

import java.util.*;

class MinMax {
    public static void main(String[] args) {
        int[][] data = {
                {3, 2, 5},
                {1, 4, 4, 8, 13},
                {9, 1, 0, 2},
                {0, 2, 6, 3, -1, -8}
        };
        System.out.println(getMaxValue(data));
        System.out.println(getMinValue(data));
    }


    public static int getMaxValue(int[][] numbers) {
        int maxValue = numbers[0][0];
        for (int j = 0; j < numbers.length; j++) {
            for (int i = 0; i < numbers[j].length; i++) {
                if (numbers[j][i] > maxValue) {
                    maxValue = numbers[j][i];
                }
            }
        }
        return maxValue;
    }

    public static int getMinValue(int[][] numbers) {
        int minValue = numbers[0][0];
        for (int j = 0; j < numbers.length; j++) {
            for (int i = 0; i < numbers[j].length; i++) {
                if (numbers[j][i] < minValue ) {
                    minValue = numbers[j][i];
                }
            }
        }
        return minValue ;
    }
}

Solution 2

I have a more fun solution using Java 8 :)

IntSummaryStatistics stats = Arrays.stream(data).flatMapToInt(Arrays::stream).collect(Collectors.summarizingInt(Integer::intValue));
int max = stats.getMax();
int min = stats.getMin();

It's a different solution than yours, obviously. But it does the same thing. To begin with, we convert the 2D array into a Stream of ints. In order to do this first we need to call flatMapToInt. We do this to stream all the elements in the array in a flat way. Imagine if we just start using a single index to iterate over the whole 2D array. It's something like that. Once we have converted the array into a stream, we will use IntSummaryStatistics in order to reuse the same stream for both min and max.

Comments

[bcsb1001]

Method references are fun: x -> Arrays.stream(x) can be simplified to Arrays::stream.

[Alexander Petrov]

You know what I find really funny. Once I started doing the Java8 thing , some things are just soo... ridiculously simple and require so much less code. I wonder how have we coded before Java 8 ?

[Admin]

Oh okay I see. Thank you so much! I've been pulling my hairs out on this one

[Admin]

Man that seems so much simpler! I suppose once I get through the beginners stuff i get to have some more fun in the future haha!

[Admin]

I was able to figure out how to find the values using a 1D array, thanks for the detail on how to declare it for a 2D array!

[Sebastian S]

Please don't just post code, but explain how this answers the question.

[Alexander Petrov]

There was a small error in the example that I corrected through the usage of IntSummaryStatistics. @Fanchen Bao pointed out a stream can be consumed only once. Therefore we use IntSummaryStatistics in order to avoid recreating the same stream for min and max.

[luckyguy73]

this code didn't work for me, however, a small change and it works by using this: Arrays.stream(gameField).flatMapToInt(Arrays::stream).summar‌​yStatistics();

[Carlos Medina]

@luckyguy73 this really helped, not sure how Alex got his code to work as I had your same problem.