JavaFX ObservableSet handle change event

import javafx.collections.FXCollections;
import javafx.collections.ObservableSet;
import javafx.collections.SetChangeListener;

public class Main {
  public static void main(String[] args) {
    // Create an observable set with two elements
    ObservableSet<String> set = FXCollections.observableSet("one", "two");
    System.out.println(set);//from ww w  . j  a v  a2 s. co m

    set.addListener((SetChangeListener.Change<? extends String> change) -> {
      System.out.println("The map has changed.");
    });

  }
}