Question

Java String search

Design and implement a recursive version of a binary search.  Instead of using a loop to repeatedly check for the target value, use calls to a recursive method to check one value at a time.  If the value is not the target, refine the search space and call the method again.  The name to search for is entered by the user, as is the indexes that define the range of viable candidates can be entered by the user (that are passed to the method). The base case that ends recursion is either finding the value within the range or running out of data to search.  The program will work on an array of sorted String objects read in from a text file.  Your program will generate an exception, that provides a message to the user, if the file can't be found or if the starting index is after the ending index.  You will create your own text file of first names in alphabetical order (binary search required ordering) to test your program, make sure to include that file with your submission.

Answer 1

If you need any clarifications kindly comment

Program

import java.io.*;
public class Main
{

public static void main(String[] args)throws Exception
{
        //File file = new File("C:\\java\\input.txt");
     
        //String file = "c:/java/input.txt";
        String[] arr={};
        int i=0;
        BufferedReader bufReader = new BufferedReader(new FileReader("C:\\java\\input.txt"));
        try
        {
        String line = bufReader.readLine();
        while (line != null)
        {
            arr[i]=line;
            line = bufReader.readLine();
        }
        }
        catch (IOException e)
        {
        e.printStackTrace();
        }
        bufReader.close();

       String x = "contribute"; //key value
       int n = arr.length;
       int result = binarySearch(arr, x,0,n-1);

       if (result == -1)
           System.out.println("Element not present");
       else
           System.out.println("Element found at index " + result);
   }

   // Returns index of x if it is present in a[], else return -1
   public static int binarySearch(String[] a, String x,int l,int r)
   {
       if (l > r)
            return -1;
       int mid = l + (r - l) / 2;
       if (a[mid].compareTo(x) < 0)
            return binarySearch(a, x, mid + 1, r);
        else if (a[mid].compareTo(x) > 0)
            return binarySearch(a, x, l, mid - 1);
        else
            return mid;
   }
}

input.txt

hello
hai
practice
java
program