In this HackerRank Java InstanceOf Keyword problem in the java programming language, you have to fix it by modifying only 3 lines! Don't add, delete or modify any extra line.

HackerRank Java Instanceof Keyword problem solution.

import java.util.*;


class Student{}
class Rockstar{   }
class Hacker{}


public class InstanceOFTutorial
{
   static String count(ArrayList mylist)
   {
      int a=0,b=0,c=0;
      for(int i=0;i<mylist.size();i++)
      {
         Object element=mylist.get(i);
         if(element instanceof Student)
            a++;
         if(element instanceof Rockstar)
            b++;
         if(element instanceof Hacker)
            c++;
      }
      String ret= Integer.toString(a)+" "+ Integer.toString(b)+" "+ Integer.toString(c);
      return ret;
   }

   public static void main(String []argh)
   {
      ArrayList mylist=new ArrayList();
      Scanner sc=new Scanner(System.in);
      int t=sc.nextInt();
      for(int i=0;i<t;i++)
      {
         String s=sc.next();
         if(s.equals("Student"))mylist.add(new Student());
         if(s.equals("Rockstar"))mylist.add(new Rockstar());
         if(s.equals("Hacker"))mylist.add(new Hacker());
      }
      System.out.println(count(mylist));
   }
}

Second solution in java8 programming.

import java.util.*;


class Student{}
class Rockstar{   }
class Hacker{}


public class InstanceOFTutorial{
	
   static String count(ArrayList mylist){
      int a = 0,b = 0,c = 0;
      for(int i = 0; i < mylist.size(); i++){
         Object element=mylist.get(i);
     if(element instanceof Student )
        a++;
     if(element instanceof Rockstar)
        b++;
     if(element instanceof Hacker)
        c++;
      }
      String ret = Integer.toString(a)+" "+ Integer.toString(b)+" "+ Integer.toString(c);
      return ret;
   }

   public static void main(String []args){
      ArrayList mylist = new ArrayList();
      Scanner sc = new Scanner(System.in);
      int t = sc.nextInt();
      for(int i=0; i<t; i++){
         String s=sc.next();
         if(s.equals("Student"))mylist.add(new Student());
         if(s.equals("Rockstar"))mylist.add(new Rockstar());
         if(s.equals("Hacker"))mylist.add(new Hacker());
      }
      System.out.println(count(mylist));
   }
}