This guide will illustrate the method to create a multi-dimensional ArrayList in Java.

## How to Create a Multi-Dimensional ArrayList in Java?

To create a multi-dimensional ArrayList in Java, users need to first declare the “**ArrayList**” with the appropriate number of dimensions. Users can do this by creating an ArrayList of ArrayLists of the desired data type.

To add an element to the multi-dimensional ArrayList, use the “**add()**” method of the inner ArrayLists. To retrieve an element from the multi-dimensional ArrayList, use the “**get()**” method of the inner ArrayLists.

**Syntax**

The syntax to create a multi-dimensional ArrayList in Java is as follows:

The description of the above syntax is enlisted below:

- The “
**DataType**” represents the type of data that will be stored in the ArrayList. - The “
**arrayList2D**” is the name of the two-dimensional ArrayList variable. - Each element of the outer “
**ArrayList**” represents a row, and each element of the inner “**ArrayList**” represents a column.

To create a 3-dimensional ArrayList, users can use the following syntax:

- The “
**arrayList3D**” is the name of the three-dimensional ArrayList variable. - The above syntax declares and initializes a three-dimensional ArrayList in Java.

**Note**: Similarly, for creating an n dimensional ArrayList, users can nest ArrayLists within ArrayLists n times.

**Example**

Here is a basic example of how to create a two-dimensional ArrayList in Java:

public class MultiDimensionalArrayListExample {

public static void main(String[] args) {

// Create a two-dimensional ArrayList of integers

ArrayList<ArrayList> twoDArrayList = new ArrayList<ArrayList>();

// Create the first row and add it to the outer ArrayList

ArrayList row1 = new ArrayList();

row1.add(1);

row1.add(2);

row1.add(3);

twoDArrayList.add(row1);

// Create the second row and add it to the outer ArrayList

ArrayList row2 = new ArrayList();

row2.add(4);

row2.add(5);

row2.add(6);

twoDArrayList.add(row2);

// Retrieve and print the value at the second row and the third column

int value = twoDArrayList.get(1).get(2);

System.out.println("Value at row 2, column 3: " + value);

}

}

The explanation of the above code is given below:

- First, create a two-dimensional ArrayList of integers called “
**twoDArrayList**”. - Then, create two inner “
**ArrayLists**” (row1 and row2) representing the rows of the two-dimensional ArrayList and add them to the outer “**twoDArrayList**” using the “**add()**” method. - Finally, retrieve and print the value at the second row and third column using the get() method of the inner ArrayLists.

**Output**

This example creates a two-dimensional ArrayList with hard-coded values.

**Note**: Users can easily modify it to add elements dynamically based on user input or other conditions.

## Conclusion

To create a multi-dimensional ArrayList in Java, first declare an ArrayList of ArrayLists with the desired number of dimensions and appropriate data type. Then, add and retrieve elements using the “**add()**” and “**get()**” methods of the inner ArrayLists. In addition, users can create a multi-dimensional ArrayList with more than two dimensions by nesting ArrayLists within ArrayLists. This article has explained the detailed explanation to create a multi-dimensional ArrayList in Java.