How to Make Multiple Threads in a Java Loop

Question

Description of the Problem

I’m making a Pokedex, in which one of its features is to filter all the Pokemons of a certain type.

I managed to implement this functionality, but the execution time is not good... It takes about 25 seconds to go through all the elements, create Pokemons objects and add them to a Vector.

I’m trying to solve this problem with the use of Threads. Instead of creating each Pokemon sequentially and adding to the vector, I am trying to create a loop that passes the position of a Jsonobject, where the Pokemon is. And after all Threads are completed I will place the resulting 'Pokemon Object' in a Vector...

My question is:

1. How do I pass this Jsonobject position;
2. How to save Threads results to a Vector, since everyone uses a space in shared memory;

Code I thought

    package model;

    import java.io.IOException;
    import java.util.Vector;

    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;

    public class Pokemon_Tipo extends RequestClass implements Runnable
    {
        private Vector<Pokemon> SameType_Pokemons = new Vector<Pokemon>();
        private JSONArray root_types;

        public Pokemon_Tipo() {}

        // Este método é chamado com o tipo de pokemon desejado
        public Vector<Pokemon> Pokemon_type(String tipo)
        {
            try
            {
                // Nesta url está os link para os pokemons do determinado tipo
                String data = get("https://pokeapi.co/api/v2/type/"+tipo);

                // Método responsável para retornar um JSONObject com as
                // informações contidadas na String data
                JSONObject root = parse(data);

                // Lista de url para todos os pokemons
                this.root_types = root.getJSONArray("pokemon");

                // loop para entrar em todos url e criar os pokemons
                for(int i=0; i<root_types.length(); i++)
                {
                    new Thread(this).start();
                }

                // Após todas as threads finalizar, retornar esse
                // vector
                // Dúvida como esperar todas as threads terminarem?
                return SameType_Pokemons;
            }

            catch (IllegalStateException | IOException | JSONException e)
            {
                e.printStackTrace();
            }

            return null;
        }

        //  Thread
        public void run()
        {
            // Pelo a URL uma posição de um JSONArray
            // Dúvida, como passo essa posição i ?
            JSONObject url = root_types.getJSONObject(i)
                    .getJSONObject("pokemon");

            // Após a Thread finalizar, salvar o resultado no Vector
            // Dúvida como salvar em um espaço compartilhado?
            SameType_Pokemons.addElement(new Pokemon(url));
        }


    }

I thought about solving this problem with Threads, in case someone has a smarter solution, I’m open to suggestions ;)