How to initialize an array in Java
Hi coders! In this tutorial, we are going to discuss a very famous data structure known as Array. Today’s topic is how to initialize an array in Java.
Array is a linear data structure which stores a set of same data in a continuous manner. Array is a very useful data structure since it can store a set of data in a manner so that any operation on the data is easy.
Array is of two types:
- One – dimensional array: This can be represented as {1, 2, 3, 5, 6} or ( a, b, g, h, e} etc.
- Two – dimensional array: This can be represented as{ {10, 11, 12, 13},{14, 15, 16, 17}}
Now to initialize array there are various ways:
To initialize array in java – primitive data type
int[] arr = new int[5] (int array declaration of size 5 )
To initialize array in java – object type
String[] strArr = new String[3]
To initialize array in java – using shortcut
int[] arr1 = {1, 2, 3, 4} (one dimentional int array)
int[] arr2 = {{1, 2, 3}, {4, 5, 6}} (two dimensional int array)
To initialize multi-dimensional array
int[][] arrMulti = new int[4][3] (2D array declaration)
Simple example of creating array of one and multiple dimensional in Java
public class ArrayInitialize { public static void main(String[] args) { // one dimensional array int[] arr1 = new int[5]; // two dimensional array int[][] arr2 = new int[4][3]; //object one dimensional array String[] strArr = new String[5]; // initialization using shortcut syntax int[] arr = {1, 2, 3}; //1D array int [][] arr = {{1,2,3},{4,5,6}}; // 2D array
There are some invalid ways of array initialization in java
int[] arr = new int[] // size of array must be there
int[] arr = new int[4][5].
Instantiating an array in java
To create an array the actual syntax is like
int[] arr = new int[5], when the new keyword is used then only the memory is allocated to array.
Example
int[] arr //declaring array
arr = new int[10] // allocating memory
Code to initialize array in Java
class ArrayInitialize { public static void main (String[] args) { // declarint an Array of integers int[] arr = new int[6]; // initialising elements one by one arr[0] = 4; arr[1] = 10; arr[2] = 30; arr[3] = 15; arr[4] = 45; arr[5] = 41; // loop to access elements for (int i = 0; i < arr.length; i++) System.out.println(" array element at index " + i + " : "+ arr[i]); } }
Output: array element at index 0 : 4 array element at index 1 : 10 array element at index 2 : 30 array element at index 3 : 15 array element at index 4 : 45 array element at index 5 : 41
Java array index is used here.
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