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a simpler question, counting instances

2 replies on 1 page. Most recent reply: Sep 11, 2003 11:50 AM by FredrikN

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Guido

Posts: 38
Nickname: kiethb
Registered: May, 2002

a simpler question, counting instances

Posted: Sep 11, 2003 11:17 AM

Is there a way to count the current number of instances of a particular class that is out there? or should I just do something like store my instances in an array and count them that way?

I am writing a multiplayer program, that if I instantiate a generic player class, I want the name to default to a ('Player ' + (numOfInstances+1)) and result to 'Player 7' for example.

thanks

FredrikN

Posts: 22
Nickname: fredrikn
Registered: Jul, 2003

Re: a simpler question, counting instances

Posted: Sep 11, 2003 11:34 AM

You can count the number of created objects with static variable(every object share the same variable

Here is one example how you can count players with a static variable

The output will be something like

$ java Driver
Number of players: 1
Number of players: 2
Number of players: 3
Number of players: 4


public class Driver
{

	public static void main(String args[])
	{
		Player p1 = new Player();
		System.out.println("Number of players: " + p1.playerCount());
		
		Player p2 = new Player();
		System.out.println("Number of players: " + p2.playerCount());
		
		Player p3 = new Player();
		System.out.println("Number of players: " + p3.playerCount());
		
		Player p4 = new Player();
		System.out.println("Number of players: " + p4.playerCount());
	
	}

}


public class Player
{
	
	private static int players = 0;
 	
	public Player()
	{
		players++;
	
	}


	public int playerCount()
	{
		return players;
	}


}

FredrikN

Posts: 22
Nickname: fredrikn
Registered: Jul, 2003

Re: a simpler question, counting instances

Posted: Sep 11, 2003 11:50 AM

Forget about the previous answer, this is a more correct way


public class Driver
{

	public static void main(String args[])
	{
		Player p1 = new Player();
		System.out.println("Number of players: " + Player.playerCount());
		
		Player p2 = new Player();
		System.out.println("Number of players: " + Player.playerCount());
		
		Player p3 = new Player();
		System.out.println("Number of players: " + Player.playerCount());
		
		Player p4 = new Player();
		System.out.println("Number of players: " + Player.playerCount());
		
	}

}


public class Player
{
	
	private static int players = 0;
 	
	public Player()
	{
		players++;
	
	}


	public static int playerCount()
	{
		return players;
	}


}

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