printing out a 2-D array in Matrix format

Question

How can I print out a simple int [][] in the matrix box format like the format in which we handwrite matrices in. A simple run of loops doesn\'t apparently work. If it helps

Answer 1

In java8 fashion:

import java.util.Arrays;

public class MatrixPrinter {

    public static void main(String[] args) {
        final int[][] matrix = new int[4][4];
        printMatrix(matrix);
    }

    public static void printMatrix(int[][] matrix) {
        Arrays.stream(matrix)
        .forEach(
            (row) -> {
                System.out.print("[");
                Arrays.stream(row)
                .forEach((el) -> System.out.print(" " + el + " "));
                System.out.println("]");
            }
        );
    }

}

this produces

[ 0  0  0  0 ]
[ 0  0  0  0 ]
[ 0  0  0  0 ]
[ 0  0  0  0 ]

but since we are here why not make the row layout customisable?

All we need is to pass a lamba to the matrixPrinter method:

import java.util.Arrays;
import java.util.function.Consumer;

public class MatrixPrinter {

    public static void main(String[] args) {
        final int[][] matrix = new int[3][3];

        Consumer noDelimiter = (row) -> {
            Arrays.stream(row).forEach((el) -> System.out.print(" " + el + " "));
            System.out.println();
        };

        Consumer pipeDelimiter = (row) -> {
            Arrays.stream(row).forEach((el) -> System.out.print("| " + el + " "));
            System.out.println("|");
        };

        Consumer likeAList = (row) -> {
            System.out.print("[");
            Arrays.stream(row)
            .forEach((el) -> System.out.print(" " + el + " "));
            System.out.println("]");
        };

        printMatrix(matrix, noDelimiter);
        System.out.println();
        printMatrix(matrix, pipeDelimiter);
        System.out.println();
        printMatrix(matrix, likeAList);

    }

    public static void printMatrix(int[][] matrix, Consumer rowPrinter) {
        Arrays.stream(matrix)
        .forEach((row) -> rowPrinter.accept(row));
    }

}

this is the result :

 0  0  0 
 0  0  0 
 0  0  0 

| 0 | 0 | 0 |
| 0 | 0 | 0 |
| 0 | 0 | 0 |

[ 0  0  0 ]
[ 0  0  0 ]
[ 0  0  0 ]