Java binary search in a ordered array of strings ArrayIndexOutOfBoundsException

Question

I am trying to implement a recursive binary search algorithm in Java.

I am looking for a string in a ordered array of strings.

Why do i get ArrayIndexOutOfBoundsException with the input "eeeeee", but not with "eeeee"?

Thank you in advance.

import java.util.Scanner;

class binarySearch{
    public static boolean recursiveBinarySearch(String[] arr, String searchTerm, int start, int end){
        int middle = start + (end-start)/2;
        if(start > end){
            return false;
        }

        if(arr[middle].equals(searchTerm)){
            return true;
        } else if(arr[middle].compareTo(searchTerm) > 0){
            return recursiveBinarySearch(arr, searchTerm, start, middle-1);
        } else if(arr[middle].compareTo(searchTerm) < 0){
            return recursiveBinarySearch(arr, searchTerm, middle+1, end);
        }
        return false;
    }

    public static void main(String[] args){

        Scanner console = new Scanner(System.in);
        String[] saved = {"aaaa","bbbb","cccc","ddddd","eeeee"};
        String searchTerm = "";
        do{
            System.out.println("Term to search in the ordered array:");
            searchTerm = console.nextLine();
        } while(searchTerm.equals(""));
        console.close();
        if(recursiveBinarySearch(saved, searchTerm, 0, saved.length)){
            System.out.println("Term found!");
        } else {
            System.out.println("Term NOT found!");
        }
    }
}

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5

Answer 1

You're passing in end as saved.length. The issue here is that .length will give you the length counting from 1, whereas arrays work with 0.

Just pass in saved.length-1 as end in recursiveBinarySearch, and you're good!

import java.util.Scanner;

class binarySearch{
    public static boolean recursiveBinarySearch(String[] arr, String searchTerm, int start, int end){
        int middle = start + (end-start)/2;
        if(start > end){
            return false;
        }

        if(arr[middle].equals(searchTerm)){
            return true;
        } else if(arr[middle].compareTo(searchTerm) > 0){
            return recursiveBinarySearch(arr, searchTerm, start, middle-1);
        } else if(arr[middle].compareTo(searchTerm) < 0){
            return recursiveBinarySearch(arr, searchTerm, middle+1, end);
        }
        return false;
    }

    public static void main(String[] args){

        Scanner console = new Scanner(System.in);
        String[] saved = {"aaaa","bbbb","cccc","ddddd","eeeee"};
        String searchTerm = "";
        do{
            System.out.println("Term to search in the ordered array:");
            searchTerm = console.nextLine();
        } while(searchTerm.equals(""));
        console.close();
        if(recursiveBinarySearch(saved, searchTerm, 0, saved.length-1)){
            System.out.println("Term found!");
        } else {
            System.out.println("Term NOT found!");
        }
    }
}