Java Multidimensional Arrays

Before we learn about the multidimensional array, make sure you know about Java array.

A multidimensional array is an array of arrays. Each element of a multidimensional array is an array itself. For example,

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

Here, we have created a multidimensional array named a. It is a 2-dimensional array, that can hold a maximum of 12 elements,

Remember, Java uses zero-based indexing, that is, indexing of arrays in Java starts with 0 and not 1.

Let's take another example of the multidimensional array. This time we will be creating a 3-dimensional array. For example,

String[][][] data = new String[3][4][2];

Here, data is a 3d array that can hold a maximum of 24 (3*4*2) elements of type String.

How to initialize a 2d array in Java?

Here is how we can initialize a 2-dimensional array in Java.

int[][] a = {
      {1, 2, 3}, 
      {4, 5, 6, 9}, 
      {7}, 
};

As we can see, each element of the multidimensional array is an array itself. And also, unlike C/C++, each row of the multidimensional array in Java can be of different lengths.

Example: 2-dimensional Array

Output:

Length of row 1: 3
Length of row 2: 4
Length of row 3: 1

In the above example, we are creating a multidimensional array named a. Since each component of a multidimensional array is also an array (a[0], a[1] and a[2] are also arrays).

Here, we are using the length attribute to calculate the length of each row.

Example: Print all elements of 2d array Using Loop

Output:

1
-2
3
-4
-5
6
9
7

We can also use the for...each loop to access elements of the multidimensional array. For example,

Output:

1
-2
3
-4
-5
6
9
7

In the above example, we are have created a 2d array named a. We then used for loop and for...each loop to access each element of the array.

How to initialize a 3d array in Java?

Let's see how we can use a 3d array in Java. We can initialize a 3d array similar to the 2d array. For example,

// test is a 3d array
int[][][] test = {
        {
          {1, -2, 3}, 
          {2, 3, 4}
        }, 
        { 
          {-4, -5, 6, 9}, 
          {1}, 
          {2, 3}
        } 
};

Basically, a 3d array is an array of 2d arrays. The rows of a 3d array can also vary in length just like in a 2d array.

Example: 3-dimensional Array

Output:

1
-2
3
2
3
4
-4
-5
6
9
1
2
3