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/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
// template pro udalosti
class EventTemplate<T extends EventListener> {
	protected List<EventListener> listeners = new ArrayList();
 
	public void addListener(T listener) {
		listeners.add(listener);
	}
 
	public void removeListener(T listener) {
		listeners.remove(listener);
	}
}
 
// deklarace udalosti pro tridu Numbers
interface NumbersListener extends EventListener {
	void numberChanged(int num);
}
 
// trida Numbers, kde pouzivam udalost/i
class Numbers
{
	public final NumberHandler event = new NumberHandler();
	private int num = 0;
 
	public void setNumber(int num) {
		this.num = num;
		event.fireNumberChanged(num);
	}
 
	// vnitřní třída handleru pro udalosti
	public class NumberHandler extends EventTemplate<NumberListener> {
		private void fireNumberChanged(int num) {
			for (NumberListener listener : listeners) {
				listener.numberChanged(num);
			}
		}
	}
}
 
class Ideone
{
	public static void main(String[] args)
	{
		Numbers n = new Numbers();
 
		n.event.addListener(new NumberListener()
		{
			@override
			public void numberChanged(int num) {
				System.out.println(num);
			}
		});
 
		// nastaví číslo a zavola udalost
		n.setnumber(100);
	}
}

Main.java:37: error: cannot find symbol
	public class NumberHandler extends EventTemplate<NumberListener> {
	                                                 ^
  symbol:   class NumberListener
  location: class Numbers
Main.java:39: error: cannot find symbol
			for (NumberListener listener : listeners) {
			     ^
  symbol:   class NumberListener
  location: class Numbers.NumberHandler
Main.java:52: error: cannot find symbol
		n.event.addListener(new NumberListener()
		                        ^
  symbol:   class NumberListener
  location: class Ideone
Main.java:61: error: cannot find symbol
		n.setnumber(100);
		 ^
  symbol:   method setnumber(int)
  location: variable n of type Numbers
Note: Main.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
4 errors

Standard output is empty