sclass SingleComponentPanel extends JPanel {
  *() { super(new BorderLayout); }

  *(Component component) {
    this();
    if (component != null) setComponent(component);
  }
  
  void set(Swingable component) {
    set(wrap(component));
  }

  void setComponent aka set(Component component) {
    swing {
      if (getComponent() == component) ret;
      
      removeAll();
      if (component != null)
        add(BorderLayout.CENTER, wrap(component));
      _revalidate(SingleComponentPanel.this);
    }
  }
  
  // Sometimes we need this?
  void setComponentAndRevalidateParent(Component component) {
    setComponent(component);
    _revalidate(_getParent(this));
  }
  
  void noComponent aka clear() { setComponent(null); }
  
  Component getComponent aka get() {
    ret swing( -> getComponentCount() == 0 ? null : getComponent(0));
  }
  
  bool isEmpty() { ret getComponent() == null; }
  bool hasComponent() { ret getComponent() != null; }
}