Array in Java

Array is a collection similar data type.  Java provides a data structure, the array, which stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Creating Arrays:

dataType[] arrayRefVar;

arrayRefVar = new dataType[arraySize];

or

dataType[] arrayRefVar = {value0, value1, ..., valuen};

Example -:   double[ ] myList = new double[10];

Types of Array in java

There are two types of array.

·         Single Dimensional Array

·         Multidimensional Array

Example of Single Dimensional array

class Testarray{  
public static void main(String args[]){  
  
int a[]=new int[5];//declaration and instantiation  
a[0]=10;//initialization  
a[1]=20;  
a[2]=70;  
a[3]=40;  
a[4]=50;  
  
//printing array  
for(int i=0;i<a.length;i++)//length is the property of array  
System.out.print(a[i]+ " ");  
  
}

Output-:  10   20    70     40     50

Multidimensional array in java

Declare of multidimensional array -: dataType[][] arrayRefVar; (or) 

dataType [][]arrayRefVar; (or) 

dataType arrayRefVar[][]; (or) 

dataType []arrayRefVar[];

Example-:  int[][] arr=new int[3][3];  //3 row and 3 column 

Initialized multidimensional array

arr[0][0]=1; 

arr[0][1]=2; 

arr[0][2]=3; 

arr[1][0]=4; 

arr[1][1]=5; 

arr[1][2]=6; 

arr[2][0]=7; 

arr[2][1]=8; 

arr[2][2]=9;

Example of multidimensional array

class Sample{  
public static void main(String args[]){  
  
//declaring and initializing 2D array  
int arr[][]={{1,2,3},{2,4,5},{4,4,5}};  
  
//printing 2D array  
for(int i=0;i<3;i++){  
 for(int j=0;j<3;j++){  
   System.out.print(arr[i][j]+" ");  
 }  
 System.out.println();  
}  
  
}
}

Example of array with using for loop

public class Sample {
 
   public static void main(String[] args) {
      double[] myList = {1.9, 2.9, 3.4, 3.5};
 
      // Print all the array elements
      for (double element: myList) {
         System.out.println(element);
      }
   }
}

Output-:

1.9

2.9

3.4

3.5

Advantage of Java Array

·         Code Optimization: It makes the code optimized, we can retrieve or sort the data easily.

·         Random access: We can get any data located at any index position.

Disadvantage of Java Array

·         Size Limit: We can store only fixed size of elements in the array. It doesn't grow its size at runtime. To solve this problem, collection framework is used in java.