Java - Best way to print 2D array? [closed]

86

votes

I was wondering what the best way of printing a 2D array was. This is some code that I have and I was just wondering if this is good practice or not. Also correct me in any other mistakes I made in this code if you find any. Thanks!

int rows = 5;
int columns = 3;

int[][] array = new int[rows][columns];

for(int i = 0; i<rows; i++)
    for(int j = 0; j<columns; j++)
        array[i][j] = 0;

for(int i = 0; i<rows; i++)
{
    for(int j = 0; j<columns; j++)
    {
        System.out.print(array[i][j]);
    }
    System.out.println();
}

javaarraysprinting

Best -- by what definition? - Hovercraft Full Of Eels

Your for loops would be safer if they used the actual array lengths. - Hovercraft Full Of Eels

Some examples in the following [SO question][1]. [1]: stackoverflow.com/questions/11383070/… - Nicolas Modrzyk

184

votes

You can print in simple way.

Use below to print 2D array

int[][] array = new int[rows][columns];
System.out.println(Arrays.deepToString(array));

Use below to print 1D array

int[] array = new int[size];
System.out.println(Arrays.toString(array));

29

votes

I would prefer generally foreach when I don't need making arithmetic operations with their indices.

for (int[] x : array)
{
   for (int y : x)
   {
        System.out.print(y + " ");
   }
   System.out.println();
}

21

votes

Simple and clean way to print a 2D array.

System.out.println(Arrays.deepToString(array).replace("], ", "]\n").replace("[[", "[").replace("]]", "]"));

11

votes

There is nothing wrong with what you have. Double-nested for loops should be easily digested by anyone reading your code.

That said, the following formulation is denser and more idiomatic java. I'd suggest poking around some of the static utility classes like Arrays and Collections sooner than later. Tons of boilerplate can be shaved off by their efficient use.

for (int[] row : array)
{
    Arrays.fill(row, 0);
    System.out.println(Arrays.toString(row));
}

8

votes

Two-liner with new line:

for(int[] x: matrix)
            System.out.println(Arrays.toString(x));

One liner without new line:

System.out.println(Arrays.deepToString(matrix));

5

votes

That's the best I guess:

   for (int[] row : matrix){
    System.out.println(Arrays.toString(row));
   }

4

votes

From Oracle Offical Java 8 Doc:

public static String deepToString(Object[] a)

Returns a string representation of the "deep contents" of the specified array. If the array contains other arrays as elements, the string representation contains their contents and so on. This method is designed for converting multidimensional arrays to strings.

3

votes

|1 2 3|
|4 5 6|

Use the code below to print the values.

System.out.println(Arrays.deepToString());

Output will look like this (the whole matrix in one line):

[[1,2,3],[4,5,6]]

2

votes

System.out.println(Arrays.deepToString(array)
                         .replace("],","\n").replace(",","\t| ")
                         .replaceAll("[\\[\\]]", " "));

You can remove unwanted brackets with .replace(), after .deepToString if you like. That will look like:

 1  |  2  |  3
 4  |  5  |  6
 7  |  8  |  9
 10 |  11 |  12
 13 |  15 |  15

2

votes

With Java 8 using Streams and ForEach:

    Arrays.stream(array).forEach((i) -> {
        Arrays.stream(i).forEach((j) -> System.out.print(j + " "));
        System.out.println();
    });

The first forEach acts as outer loop while the next as inner loop

2

votes

@Ashika's answer works fantastically if you want (0,0) to be represented in the top, left corner, per standard matrix convention. If however you would prefer to put (0,0) in the lower left hand corner, in the style of the standard coordinate system, you could use this:

LinkedList<String> printList = new LinkedList<String>();
for (char[] row: array) {
    printList.addFirst(Arrays.toString(row));;
}
while (!printList.isEmpty())
    System.out.println(printList.removeFirst());

This used LIFO (Last In First Out) to reverse the order at print time.

0

votes

Try this,

for (char[] temp : box) {
    System.err.println(Arrays.toString(temp).replaceAll(",", " ").replaceAll("\\[|\\]", ""));
}

0

votes

Adapting from https://stackoverflow.com/a/49428678/1527469 (to add indexes):

System.out.print(" ");
for (int row = 0; row < array[0].length; row++) {
    System.out.print("\t" + row );
}
System.out.println();
for (int row = 0; row < array.length; row++) {
    for (int col = 0; col < array[row].length; col++) {
        if (col < 1) {
            System.out.print(row);
            System.out.print("\t" + array[row][col]);
        } else {

            System.out.print("\t" + array[row][col]);
        }
    }
    System.out.println();
}

0

votes

class MultidimensionalArray {
    public static void main(String[] args) {

        // create a 2d array
        int[][] a = {
                {1, -2, 3},
                {-4, -5, 6, 9},
                {7},
        };

        // first for...each loop access the individual array
        // inside the 2d array
        for (int[] innerArray: a) {
            // second for...each loop access each element inside the row
            for(int data: innerArray) {
                System.out.println(data);
            }
        }
    }
}

You can do it like this for 2D array

Java - Best way to print 2D array? [closed]

14 Answers