Multi-Dimensional Arrays

Introduction

• This page assumes you are familar with one-dimensional arrays
• Java supports multi-dimensional arrays.
• A two-dimensional array can be thought of as an array of arrays.
  • A 2D array is also known as a matrix.
  • The size of the 2D array is specified by a height and width.

int[][] matrix = new int[4][3];

Produces a matrix with height of 4 and width of 3.

matrix[0][0] = 1;
matrix[0][1] = 2;
matrix[0][2] = 3;
matrix[3][1] = 9;

Modifies the matrix like this:

We can get determine the height and width of a 2D array as follows.

final int height = matrix.length;
final int width = matrix[0].length;

Example

The following method finds the largest value in the matrix.

public static double max(double[][] matrix) {
    double max = Double.MIN_VALUE;
    for(int row = 0; row < matrix.length; row++) {
        for(int col = 0; col < matrix[0].length; col++) {
            max = Math.max(max, matrix[row][col]);
        }
    }
    return max;
}