Introduction

What is a 2D Array?

We’ve already learned plenty about arrays. We know that an array can hold many different types (integers, strings, doubles, etc.), but how about an array that holds arrays?

A 2D array has a type such as int[][] or String[][], with two pairs of square brackets. The elements of a 2D array are arranged in rows and columns, and the new operator for 2D arrays specifies both the number of rows and the number of columns. For example,

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

This creates a 2D array of int that has 12 elements arranged in 3 rows and 4 columns. There are also initializers for 2D arrays. For example, this statement creates the 3-by-4 array that is shown in the picture below:

int[][] A = {    
                {  1,  0, 12, -1 },
                {  7, -3,  2,  5 },
                { -5, -2,  2, -9 }
            };

An array initializer for a 2D array contains the rows of A, separated by commas and enclosed between braces. Each row, in turn, is a list of values separated by commas and enclosed between braces. There are also 2D array literals with a similar syntax that can be used anywhere, not just in declarations. For example,

A = new int[][] { 
                    {  1,  0, 12, -1 },
                    {  7, -3,  2,  5 },
                    { -5, -2,  2, -9 }
                };

All of this extends naturally to three-dimensional, four-dimensional, and even higher-dimensional arrays.