How to Write Code for Matrix in Java

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,

2-dimensional Array

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.

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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.

Initialization of 2-dimensional Array

Example: 2-dimensional Array

          class MultidimensionalArray {     public static void main(String[] args) {          // create a 2d array         int[][] a = {             {1, 2, 3},              {4, 5, 6, 9},              {7},          };                // calculate the length of each row         System.out.println("Length of row 1: " + a[0].length);         System.out.println("Length of row 2: " + a[1].length);         System.out.println("Length of row 3: " + a[2].length);     } }        

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.

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Example: Print all elements of 2d array Using Loop

          class MultidimensionalArray {     public static void main(String[] args) {          int[][] a = {             {1, -2, 3},              {-4, -5, 6, 9},              {7},          };                for (int i = 0; i < a.length; ++i) {             for(int j = 0; j < a[i].length; ++j) {                 System.out.println(a[i][j]);             }         }     } }        

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,

          class MultidimensionalArray {     public static void main(String[] args) {          // create a 2d array         int[][] a = {             {1, -2, 3},              {-4, -5, 6, 9},              {7},          };                // first for...each loop access the individual array         // inside the 2d array         for (int[] innerArray: a) {             // second for...each loop access each element inside the row             for(int data: innerArray) {                 System.out.println(data);             }         }     } }        

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.

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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.

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Example: 3-dimensional Array

          class ThreeArray {     public static void main(String[] args) {          // create a 3d array         int[][][] test = {             {               {1, -2, 3},                {2, 3, 4}             },              {                {-4, -5, 6, 9},                {1},                {2, 3}             }          };          // for..each loop to iterate through elements of 3d array         for (int[][] array2D: test) {             for (int[] array1D: array2D) {                 for(int item: array1D) {                     System.out.println(item);                 }             }         }     } }        

Output:

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

How to Write Code for Matrix in Java

Source: https://www.programiz.com/java-programming/multidimensional-array

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