Java Multi-Dimensional Array

 Array - In computer science, an array is a collection of objects with same data type or we can say array as a container that can hold a fixed number of objects. Example: Below we can see an array containing 7 integer values and index is starting from 0.

Image a: Array Representation

Properties of array:

• Array is simplest, most used data structure and used for implementing other data structures as list, stacks, queues etc.
• Data type must be same.
• Length is fixed.
• Length must be specified during array initialization.
• Each object stored at an index.
• Array index starts from zero.
• Object can be retrieved directly by index number.

Types of array:

• One-dimensional array - 1-D or single dimensional array is a linear array, they can represent any row or column.
  Example : int arr = new int[5];
• Multi-dimensional array - Multi-Dimensional array is an array of array like 2-D array, 3-D array. Each element of multi-dimensional array is an array. Below we have an example of 2-D array in JAVA which can hold 9 elements, a 2D array holds rows and columns both and index always starts from 0. lets see:
  Example: int[][] a = new int[3][3];
  
  
  
  Image b: 2-D Array
• Java Code for 2-D array:
  

  
  public class TwoDimensionalArray {
      public static void main(String[] args) {
          /*
          Declaration and initialization of array
          int [][] array;
          int[][] a = new int[3][3];
          int[][] b = new int[][]{
              {3, 3, 5},
              {2, 6, 1},
              {5, 7, 8},
          };*/
          int[][] arr = {
                  {3, 3, 5},
                  {2, 6, 1},
                  {5, 7, 8},
          };
          /*
          * printing multi dimensional array with old technique
          for (int i = 0; i < arr.length; i++) {
              for (int j = 0; j < arr[i].length; j++) {
                  System.out.print(arr[i][j] + " ");
              }
              System.out.print(" \n");
          }
          */
          /* Printing multi dimensional array with for...each loop */
          for (int[] innerArray : arr) {
              for (int data : innerArray) {
                  System.out.print(data + " ");
              }
              System.out.print(" \n");
          }
      }
  }
  

  Output:
  

  
  3 3 5  
  2 6 1  
  5 7 8  

• Java Code for 3-D array:
  

  
  public class ThreeDimensionalArray {
      public static void main(String[] args) {
          /*
          Declaration and initialization of array
          int [][][] array;
          int[][][] a = new int[3][3][3]; // total 27 elements can be stored
          int[][][] b = new int[][][]{
                  {
                          {3, 3, 5},
                          {2, 6, 1}
                  },
                  {
                          {-3, -3, -5},
                          {-2, -6, -1}
                  }
          };*/
          int[][][] arr = {
                  {
                          {3, 3, 5},
                          {2, 6, 1},
                          {8, 4, 7}
                  },
                  {
                          {-3, -3, -5},
                          {-2, -6, -1},
                          {-8, -4, -7}
                  },
                  {
                          {3, 3, 5},
                          {2, 6, 1},
                          {8, 4, 7}
                  }
          };
          /** printing multi dimensional array with old technique
          for (int i = 0; i < arr.length; i++) {
              for (int j = 0; j < arr[i].length; j++) {
                  for (int k = 0; k < arr[i].length; k++) {
                      System.out.print(arr[i][j][k] + " ");
                  }
                  System.out.print(" \n");
              }
              System.out.print(" \n");
          }*/
          /* Printing multi dimensional array with for-each loop */
          for (int[][] outerArray : arr) {
              for (int[] innerArray : outerArray) {
                  for (int data : innerArray) {
                      System.out.print(data + " ");
                  }
                  System.out.print(" \n");
              }
              System.out.print(" \n");
          }
      }
  }
  

  Output:
  

  
  3 3 5  
  2 6 1  
  8 4 7  
   
  -3 -3 -5  
  -2 -6 -1  
  -8 -4 -7  
   
  3 3 5  
  2 6 1  
  8 4 7  

Most Important Interview Questions of Array- 

1. Two Sum Problem - Question with Optimal and Brute Force Solution
2. Container with most water Problem - Question with Optimal and Brute Force Solution
3. Trapping Rainwater Problem - Question with Optimal Solution, Brute Force Solution