Two Dimensional Array in Java

Today we will look into Two-dimensional array in java. An array is like a container that can hold a certain number of values.

Two Dimensional Array in Java

Let’s look at a few examples of defining java two-dimensional array or 2d array.

Java Two Dimensional Array of primitive type

int[][] arr = new int[2][3];
for (int i = 0; i < arr.length; i++) {
	for (int j = 0; j < arr[i].length; j++) {
		arr[i][j] = j;
		System.out.print(arr[i][j] + " ");
	}
	System.out.println("");
}

Java Two Dimensional Array of Objects

String[][] arrStr = new String[3][4];
for (int i = 0; i < arrStr.length; i++) {
	for (int j = 0; j < arrStr[i].length; j++) {
		arrStr[i][j] = "Str" + j;
		System.out.print(arrStr[i][j] + " ");
	}
	System.out.println("");
}

So we can define a two dimensional array of primitive data types as well as objects. If you look at the above examples, two dimensional array looks like a matrix, something like below image.

However, in Java, there is no concept of a two-dimensional array. A two-dimensional array in java is just an array of array. So below image correctly defines two-dimensional array structure in java.

Java multidimensional array example

Now if two-dimensional array in java is an array-of-arrays, then it should also support non-symmetric sizes as shown in below image.

Well, it’s absolutely fine in java. Below is an example program that depicts above multidimensional array.

public class MultidimensionalArrayExample {

	public static void main(String[] args) {

		// creating and initializing two dimensional array with shortcut syntax
		int[][] arrInt = { { 1, 2 }, { 3, 4, 5 } };
		for (int i = 0; i < arrInt.length; i++) {
			for (int j = 0; j < arrInt[i].length; j++) {
				System.out.print(arrInt[i][j] + " ");
			}
			System.out.println("");
		}

		// showing multidimensional arrays initializing
		int[][] arrMulti = new int[2][]; // yes it's valid

		arrMulti[0] = new int[2];
		arrMulti[1] = new int[3];

		arrMulti[0][0] = 1;
		arrMulti[0][1] = 2;
		arrMulti[1][0] = 3;
		arrMulti[1][1] = 4;
		arrMulti[1][2] = 5;
		for (int i = 0; i < arrInt.length; i++) {
			for (int j = 0; j < arrInt[i].length; j++) {
				System.out.print(arrInt[i][j] + " ");
			}
			System.out.println("");
		}
	}
}

If we run the above program, it will produce the following output.

1 2 
3 4 5 
1 2 
3 4 5 

That’s all about two-dimensional array in java. In a similar way, we can define a multidimensional array in java too.

Reference: Java Array Oracle page