Binary Search in Java

☞To use this technique elements of an array must be in ascending or descending order.

☞Procedure :

First find the middle element of the array.

Compare the middle element with the desired item. 
After this step there are three cases:

1) If middle element is the desired item,
   then search is successful.
   if(arr[middle])==numSearch)
        
2) If middle element is less than the desired item,
   then search the second half of the array.
   first=middle+1;
        
3) If middle element is greater than the desired item,
   then search the first half of the array.
   last=middle-1;

Example 

import java.util.*;
class BinarySearch{
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
            
        System.out.println("Enter the size");
        int size=sc.nextInt();
            
        int arr[]=new int[size];
            
        int i, numSearch, flag=1;
        System.out.println("Enter the elements");
        for(i=0;i<arr.length;i++)
            arr[i]=sc.nextInt();
            
        System.out.println("Enter the number to be searched");
        numSearch=sc.nextInt();
        
        int first=0;
        int last=size-1;
        int middle;
        
        while(first<=last){
            
            middle=(first+last)/2;
            
            if(numSearch==arr[middle]){
                flag=0;
                break;
            }
            else if(numSearch>arr[middle])
                first=middle+1;
            else
                last=middle-1;
        
        }
        
        if(flag==0)
            System.out.println("The number is present");
        else
            System.out.println("The number is not present");
    
    }			    
}

Output

Enter the size
5
Enter the elements
10
20
30
40
50
Enter the number to be searched
66
Ther number is not present