Exception in thread “main” java.lang.ArrayIndexOutOfBoundsException:

Question

So my assignment is write a recursive Java method that finds the maximum of an array of integers without using any loops. The input is a first line that contains a single integer n < 10. The next line contains n numbers separated by spaces. The output should be a single integer. Call your program FindMax. The below code is what I have so far, it compiles but instead of me being able to enter

input line 1: 5 (n) } 

This is what I need to be able to input

input line2: 2 3 4 5 3 }

it makes me enter

input: 5 (n)
input: 2
input: 3
input: 4
input: 5
input: 3

also after entering the above I get:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
at FindMaxtesting.getmax(FindMaxtesting.java:35)
at FindMaxtesting.getmax(FindMaxtesting.java:48)
at FindMaxtesting.getmax(FindMaxtesting.java:42)
at FindMaxtesting.getmax(FindMaxtesting.java:42)
at FindMaxtesting.getmax(FindMaxtesting.java:42)
at FindMaxtesting.getmax(FindMaxtesting.java:42)
at FindMaxtesting.main(FindMaxtesting.java:17)

This is my code so far:

import java.util.Scanner;

public class FindMaxtesting
{
   public static void main (String[]args)
   {
  Scanner sc = new Scanner(System.in);
  int n = sc.nextInt(); 
  int i = 0;
  int fin = 0;
  System.out.println(getmax( Inca(n ) , n , fin , i));
   }

   public static int[] Inca(int n )
   {
  Scanner sc = new Scanner(System.in);
  int[] arr = new int[n];
  for(int j=0;j<n;++j)
  {
     arr[j] = sc.nextInt();
      }
      return arr;   
   }    

   public static int getmax ( int arr[], int n, int fin, int i )
   {
      int temp = 0;
      if (fin < arr[i])
      {
         temp = fin;
     fin = arr[i];
     arr[i] = temp;
     i++;
     getmax(arr , n , fin , i);
      }

      else if (fin > arr[i])
      {
         i++;
     getmax(arr , n , fin , i);
      }

      else if ( i == n-1 )
      {
         return fin;
      }
      return fin;
   }
}

Answer 1

The essence of your problem is that in getmax you need to add the lines

if (i >= n)
    return fin;

You are searching through the array recursively, which isn't really the best way to do it, but I assume that this is a homework problem, and you need to say when to stop looking further through the array, however you continue to look further in the array. When i>=n then you know you have searched the entire array, and can just return fin, as there are no further values that can be greater.