SingleTon

1. what is singleton patten
    Singleton adalah salaha satu konsep dari Desing pttern yang menangani       masalah khususnya pada saat kita membuat instansi dalam sebuah class.
2. what are their benefit
    Seorang Programmer tidak perlu lagi membuat objek atau instansi berulang kali.
3. what are their drawback
    Setau saya kelemahan Singleton hanya satu yatu terjadi pemborosan proses pada pengecekan if(instance == null){}.
4. when to use it at best
    Singleton digunakan apabila kita ingin membatasi bahwa hanya boleh ada sebuah instance class dalam aplikasi.
5. when to NOT use it
    Singleton tidak digunakan kalau kita tidak ingin membatasi class instance dalam aplikasi.

* Class Main
public class ScrabbleTestThread
{
    public static void main(String[] args)
    {
        Runnable getTiles = new GetTheTiles();
        Runnable getTilesAgain = new GetTheTiles();

        new Thread(getTiles).start();
        new Thread(getTilesAgain).start();
    }
}

* Class Utama
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedList;

public class Singleton
{
    private static Singleton firtsInstance = null;

    String[] scrabbleLetters = {"a","a","a","a","a","a","a","a","a",
                                "b","b","b","b","b","b","b","b","b",
                                "c","c","c","c","c","c","c","c","c",
                                "d","d","d","d","d","d","d","d","d",
                                "e","e","e","e","e","e","e","e","e",
                                "f","f","f","f","f","f","f","f","f",
                                "g","g","g","h","h","h","i","i","i",
                                "j","j","j","k","k","k","l","l","l",
                                "m","m","m","n","n","n","o","o","o",
                                "p","p","p","w","w","w","x","x","x",
                                "y","y","y","z","z","z","z","z","z"};

    private LinkedList<String> letterList = new LinkedList<String>(Arrays.asList(scrabbleLetters));

    static boolean firstThread = true;

    private Singleton()
    {

    }

    public static Singleton getInstance()
    {
        if(firtsInstance == null)
        {
            if(firstThread)
            {
                firstThread = false;

                Thread.currentThread();
                try
                {
                    Thread.sleep(1000);
                }catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
            }

            synchronized (Singleton.class)
            {
                if(firtsInstance == null)
                {
                    firtsInstance = new Singleton();
                    Collections.shuffle(firtsInstance.letterList);
                }
            }

        }
        return firtsInstance;
    }


    public LinkedList<String> getLetterList()
    {
        return firtsInstance.letterList;
    }

    public LinkedList<String> getTiles(int howManyTiles)
    {
        LinkedList<String> tilesToSend = new LinkedList<String>();

        for(int i = 0; i <= howManyTiles; i++)
        {
            tilesToSend.add(firtsInstance.letterList.remove(0));
        }
        return tilesToSend;
    }
}

* Class Method
 import java.util.LinkedList;

public class GetTheTiles implements Runnable
{

    public void run()
    {
        Singleton newInstance = Singleton.getInstance();
        System.out.println("============ID1============");
        System.out.println("Instance ID 1 : "+System.identityHashCode(newInstance));

        System.out.println(newInstance.getLetterList());

        LinkedList<String> playerOneTiles = newInstance.getTiles(7);


            System.out.println("Player 1 : " + playerOneTiles);
            System.out.println("Got Tiles");

    }
}