How can I do binary search in java ArrayList<Long>?

Question

I am trying to make binary search in ArrayList, but the binarySearch method does not work for Long, as well as Double and Float. My code is

import java.util.*;

 public class BinarySearchInArrayList
 {
     public static void main(String[]args)
     {
         ArrayList<Long> ar = new ArrayList();

         for(long l = 1;l<100000;l++)
         {
             ar.add(l);
         }

         System.out.println("arraylist: "+ar); 
         System.out.println("Which number's index do you want to know? ");
         Scanner scan = new Scanner(System.in);
         int p = scan.nextInt();
         int index = Collections.binarySearch(ar,p);
         System.out.println("number "+p+" has index "+index);
     }

When I use Integer instead of Long , it works fine, but I want to make it with Long . Can you help me, please?

Answer 1

int p = scan.nextInt();
int index = Collections.binarySearch(ar,p);

Above should be:

long index = Collections.binarySearch(ar,p);
long p = scan.nextLong();

Answer 2

I'd recommend using Apache's ArrayUtils for this:

http://commons.apache.org/proper/commons-lang/javadocs/api-2.3/org/apache/commons/lang/ArrayUtils.html

It offers this method:

static int  indexOf(long[] array, long valueToFind, int startIndex)

Which finds the index of the given value in the array starting at the given index.