Sorting 2D Array in Java

In this tutorial, we will learn how to sort a 2D array in Java. As we know, a 2D array consists of rows and columns, thus we can sort the 2D array column-wise or row-wise, we will see both the programs.

1. Sorting 2D Array Column-wise

In the following program, we are sorting the given 2D array column-wise, this means that each column of the array needs to be sorted individually.

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // 2D Array
        int[][] array = {
            {5, 2, 9},
            {1, 3, 7},
            {4, 0, 8}
        };

        // Displaying the elements of original array
        System.out.println("Original array:");
        print2DArray(array);

        // Sort each column of 2D Array
        sortColumns(array);

        // Displaying the elements of sorted array
        System.out.println("\nArray sorted column-wise:");
        print2DArray(array);
    }

    // Method to sort each column of the 2D array
    public static void sortColumns(int[][] array) {
        int numRows = array.length;
        int numCols = array[0].length;

        for (int col = 0; col < numCols; col++) {
            // Extract the column into a temporary array
            int[] columnArray = new int[numRows];
            for (int row = 0; row < numRows; row++) {
                columnArray[row] = array[row][col];
            }

            // Sort the temporary array
            Arrays.sort(columnArray);

            // Write the sorted values back into the column
            for (int row = 0; row < numRows; row++) {
                array[row][col] = columnArray[row];
            }
        }
    }

    // This method prints the 2D array
    public static void print2DArray(int[][] array) {
        for (int[] row : array) {
            System.out.println(Arrays.toString(row));
        }
    }
}

Output:

Original array:
[5, 2, 9]
[1, 3, 7]
[4, 0, 8]

Array sorted column-wise:
[1, 0, 7]
[4, 2, 8]
[5, 3, 9]

2. Sorting 2D Array Row-wise

In the following program, we are sorting the given 2D array row-wise, this means that each row of the array needs to be sorted individually.

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // 2D Array
        int[][] array = {
            {5, 2, 9},
            {1, 3, 7},
            {4, 0, 8}
        };

        // Displaying the elements of original array
        System.out.println("Original array:");
        print2DArray(array);

        // Sort each row of 2D Array
        sortRows(array);

        // Displaying the elements of sorted array
        System.out.println("\nArray sorted row-wise:");
        print2DArray(array);
    }

    // Method to sort each row of the 2D array
    public static void sortRows(int[][] array) {
        for (int[] row : array) {
            Arrays.sort(row);
        }
    }

    // This method prints the 2D Array
    public static void print2DArray(int[][] array) {
        for (int[] row : array) {
            System.out.println(Arrays.toString(row));
        }
    }
}

Output:

Original array:
[5, 2, 9]
[1, 3, 7]
[4, 0, 8]

Array sorted row-wise:
[2, 5, 9]
[1, 3, 7]
[0, 4, 8]