java array define code example

Example 1: how to declare array java

int intArray[];    //declaring array
intArray = new int[20];  // allocating memory to array
//OR
int[] intArray = new int[20]; // combining both statements in one

Example 2: arrays in java

3 data structures:
1. Array 2. Collection 3. Maps            
Arrays: a variable that can have multiple data    
DataType[]  variableName = { dat1, data2, data3 };
the data we are storing MUST match with DataTyp
each data in the array has its own index number

initializing the size of the array:
1. giving the values: size will be initialized automatically
	int[] arr = {10, 20, 30};
2. giving the size only: default value of the datatype will be assigned at each index
			                  int[] arr = new int[length];
			                  int[] arr = new int[5];
default values: byte, short, int, long ==> 0
			String or any object ==> null                        
length: returns the length of array
Array' size is fixed
Arrays utilities:
length: returns total number of the element of the arra
Arrays Utilities:
 Arrays class:  presented in "java.util"
             import java.util.Arrays;
 
Arrays.toString(arrayName): converts the array to String, returns the string
Arrays.sort(arrayName): sorts the given array in ascending order                    
Arrays.equals(arr1, arr2): chekcs if the two arrays are same or not. returns boolean 
 toCharArray(): returns char array from the string
String str = "Batch 18";
char[] ch   = str.toCharArray(); //['B', 'a', 't', 'c', 'h', ' ', '1', '8']

Array: size is fixed
       supports primitives and objects
       Can be multi-dimensional
       has index, accept duplicates
       Arrays.sort(arrayName);
       Collections.sort()