arrayin java

An array is an ordered collection of elements of the same type, identified by a pair of square brackets []. To use an array, you need to: 1. Declare the array with a name and a type. Use a plural name for array, e.g., marks, rows, numbers. All elements of the array belong to the same type. 2. Allocate the array using new operator, or through initialization, e.g. int[] marks; // Declare an int array named marks // marks contains a special value called null. int marks[]; // Same as above, but the above syntax recommended marks = new int[5]; // Allocate 5 elements via the "new" operator // Declare and allocate a 20-element array in one statement via "new" operator int[] factors = new int[20]; // Declare, allocate a 6-element array thru initialization int[] numbers = {11, 22, 33, 44, 55, 66}; // size of array deduced from the number of items

//method 1 int[] age = new int[3]; age[0] = 1; age[1] = 3; age[2] = 6; for (int i=0; i < 3; i++) System.out.println(age[i]); //method 2 int[] num = {3,3,5}; //int num[] = {3,3,5}; also works the same System.out.println(num[0]);

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()

Posted by: Guest on May-28-2021

For example: int[ ] num = new int[6]; public class AccessingArrayElements { public static void main(String[] args) { int[] arrNum = {25, 23, 15, 20, 24}; for(int a = 0; a < arrNum.length; a++) { System.out.println(arrNum[a]); } } }

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