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Beatriz Maciel
Beatriz Maciel

Posted on • Edited on

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HackerRank #23 | Instanceof keyword | 🇧🇷

Essa publicação é só para explicar um objeto simples (mas que eu não conhecia) chamado instanceof. A sua tradução para português seria "é um" ou "é uma" e é usado como um construtor/identificador.

Neste problema do HackerRank, ele pede para que, em três linhas, você consiga dizer que um element é Student, Rockstar ou Hacker. Como já existem essas classes declaradas, basta escrevermos dentro do if que cada um desses elementos é uma dessas classes.

=========

Sendo assim, o que é implementado dessa forma:

         if(element instanceof Student)
            a++;
         if(element instanceof Rockstar)
            b++;
         if(element instanceof Hacker)
            c++;
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Pode ser também lido dessa forma:

         if(element é um Student)
            a++;
         if(element é um Rockstar)
            b++;
         if(element é um Hacker)
            c++;
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=========

O código final fica assim:

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));
   }
}
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=========

Referências

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Essa publicação faz parte de uma série de exercícios resolvidos em Java no HackerRank. Acesse a série completa:

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Top comments (0)

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