Access 3D Arrays

How do you access elements?

Following is a simple sketch of a 3D array A with a capacity of D layers, N rows, and M columns.

int[][][] A;

Visual representation

  A[layer][row][column]
     ↓     ↓      ↓
   depth  rows  columns

Since arrays in Java start from the 0th index in all dimensions:

• If you want to access the first element, you need to use A[0][0][0]
• To access an element at layer 1, row 2, column 1: A[1][2][1]
• To access the last element in a D×N×M array: A[D-1][N-1][M-1]

What happens with invalid indexes?

What happens if we try A[3][2][1], A[1][5][2], or A[2][1][4] in a 2×3×3 array? 🤔

You guessed it. We run into ArrayIndexOutOfBoundsException.

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 2
at ThreeDimensionalArray.main(ThreeDimensionalArray.java:15)

You can access and modify individual elements in a 3D array using the layer, row, and column indexes.

For example, to access the element at layer 1, row 2, and column 1 of the "cube" array:

int element = A[1][2][1];

Similarly, you can assign a value to an element in the array:

A[1][2][1] = 42;

At most, we can access the last element of the array using A[D-1][N-1][M-1].