class Ideone {
  public static void main(final String[] args) {
    final Ideone thing = new Ideone();
    System.out.println(thing.leaves);
    thing.foo(thing);
    System.out.println(thing.leaves);
  }

  private int leaves;

  public Ideone() {
  }

  public void foo(Ideone this, final Ideone self) {
    this.leaves++;
    self.leaves++;
  }
}