Java 2d Arrays — Free Java Tutorial

TL;DR: Learn Java 2d Arrays in Java with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Java 2d Arrays in Java

A 2D array in Java is an array of arrays. Declare with: int[][] matrix = new int[rows][cols]; or using an initialiser: int[][] m = {{1,2},{3,4}};

Access elements with two indices: matrix[row][col]. Rows and columns are zero-indexed.

Iterate with nested loops: outer loop over rows (i), inner loop over columns (j). matrix.length gives the number of rows; matrix[0].length gives the number of columns.

Java supports jagged arrays (rows of different lengths) since each row is a separate array object.

// Declaration
int[][] matrix = new int[3][4];   // 3 rows, 4 cols
int[][] grid   = {{1,2,3},{4,5,6},{7,8,9}};

// Access
int val = grid[1][2];  // row 1, col 2 = 6

// Iterate
for (int i = 0; i < matrix.length; i++)
    for (int j = 0; j < matrix[i].length; j++)
        matrix[i][j] = i * matrix[i].length + j;

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