Multi Dimensional Array

A two-dimensional array is an array whose elements are arrays. It is commonly used to represent rows and columns, such as a marks sheet, seating plan, grid, or matrix.

Create a matrix

Run this example to see its output.

marks[0][1] means row 0, then column 1. It returns 81 in this example.

Traverse rows and columns

Run this example to see its output.

Use marks[row].length rather than assuming every row has the same number of columns. This works for both rectangular and jagged arrays.

Calculate a matrix total

Run this example to see its output.

This uses nested enhanced for loops. The outer loop gives one row at a time; the inner loop gives every value from that row.

Rectangular versus jagged

Java does not require a two-dimensional array to be rectangular. A jagged array is covered in the next lesson.

What to remember

• A two-dimensional array is an array of arrays.
• The first index selects a row; the second selects a value in that row.
• array.length is the row count, while array[row].length is the current row's size.
• Nested loops are the normal way to visit every cell.