ModelObservable.java

import java.util.LinkedList;
import java.util.List;
import java.util.Iterator;

public abstract class ModelObservable {
	private List observers=new LinkedList();
	  
	public void attach(ModelObserver o){
		if (o == null) {
      		throw new IllegalArgumentException("Parameter is null");
    	}
    	observers.add(o);
  	}
  
  	public void detach(  ModelObserver o){
    	if (o == null) {
      		throw new IllegalArgumentException("Parameter is null");
    	}
    	observers.remove(o);
  	}
  	
  	public void notifyObservers(){
    	Iterator it = observers.iterator();
    	while(it.hasNext()) {
    		ModelObserver x;
    		x = (ModelObserver) it.next();
      		x.update();
    	}
  	}
  	public abstract void nextGeneration();
  
  	public abstract int[][] getPlayground();
  	
  	public abstract void setLifeform(  int coord,  int coord2,  int i);
  	
  	public abstract void setPlayground(  int[][] pg);
}