Array in Java with Examples | Tutorials- Scratcharound

Apple [ ] apples = new Apple[5];
While constructing an array we also define the number of elements it can have, which defines the memory allocated for that array in the heap memory. We write the number of elements array can have inside the square brackets as shown in the above syntax.
Note: Note that in above statement we have declared and constructed the array in a single statement, which is perfectly legal.
Notice that in the above apples array we constructed, no object of Apple has been created but only the empty references inside the Apples array. We can use these references to point to some Object of type Apple on the heap.
Constructing and initializing an one dimensional array in java:
We can also construct an array an initialize it simultaneously -
int [ ] arr = {1,3,40,3}
Above statement will create an array of integers have the elements specified inside the curly braces and with size 4(no of elements inside the curly braces).

Creating Multidimensional Array In Java

In java a multidimensional array is an array of arrays, ie. each element of the array will hold the reference to some another array. For example a 2 dimensional array, will have elements with each element holding the reference to some other array on the heap, an that another array will hold the actual values.
Example :

int arr [  ][  ] = new int [3][  ]
arr[0] = new int[2];
arr[0][0] = 3;
arr[0][1] = 9

arr[1] = new int[1]
arr[1][0] = 8;

Explained: Above 2-D array arr is of size 3 and has referene to another arrays on each of its index 0 and 1, while index 3 has nothing yet.
Index of an array always starts with zero, so if we have a array of length 8 then the index will start at 0 and will end at 7.

What we can put inside an array of some specific type(int [ ], String [ ], Apple [ ] and others)

Array of primitives:
An primitive type array can accept any type of value that can be accepted by the declared type,for example -
We can put a byte ,char or short inside an primitive array of type int, because these values can be accepted by an integer type.
Example:

int [  ]arr = new int[4];
short s = 2;
int i = 12;
byte b = 1;

arr[0] = s;
arr[1] = i;
arr[2] = b;

Array of Object References:
In an array of Object references can accept object of any subclass of the declared class;
Example:

Fruit [  ] fruits = new Fruit[4];
Apple extends Fruit {};
Mango extends Fruit {};

fruits[0] = new Apple();
fruits[1] = new Mango();

Array Of Interface Type - Like array of class type, an array of interface type can accept any object which implements that Interface.

Accessing Array elements

We can easily get the elements inside an array by using the index of that element -

int arr[  ] = {12, 1, 20, 120};
int i = arr[2];
System.out.println(i);

above code will print the element at index 2 - 20
Loop Through an Array:
We can loop through the array elements by running the loop through its length.
We can get the array length by using length property of array - arr.length;
Example:

package com.array;

public class HelloArray {

 public static void main(String[  ] args) {
  int [  ] arr = {1,2,30,20};
  for(int i=0; i< arr.length ;i ++){
   System.out.print(arr[i]+ " ");
  }
 }
}

Output: 1 2 30 20
or we can use enhanced for loop-
Example:

package com.array;

public class HelloArray {

 public static void main(String[  ] args) {
  int [  ] arr = {1,2,30,20};
  for(int i : arr){
   System.out.print(i+" ");
  }
 }
}

This was some important and deep information about arrays in java, we can also use ArrayList in java if we don't know the exact number of elements we are going to insert inside it to store Objects. We will learn about ArrayList in our next articles. If you have any questions, feel free to ask it in the comment box below.