Looking at the JavaDocs for TableColumn you see this:

 firstNameCol.setCellValueFactory(new Callback<CellDataFeatures<Person, String>, ObservableValue<String>>() {
     public ObservableValue<String> call(CellDataFeatures<Person, String> p) {
         return new ReadOnlyObjectWrapper(p.getValue().getFirstName());
     }
  });

The idea being to convert a String value into a read only Observable that can be passed to a cell.

However, looking at the JavaDocs for ReadOnlyObjectWrapper, you see this:

This class provides a convenient class to define read-only properties. It creates two properties that are synchronized. One property is read-only and can be passed to external users. The other property is read- and writable and should be used internally only.

The class itself extends from SimpleObjectProperty and only adds one method, getReadOnlyProperty(), which you can see is not called in the TableColumn example.

Looking at the TableColumn source code (JFX 21) you can see this:

public final ObservableValue<T> getCellObservableValue(S var1) {
        Callback var2 = this.getCellValueFactory();
        if (var2 == null) {
            return null;
        } else {
            TableView var3 = this.getTableView();
            if (var3 == null) {
                return null;
            } else {
                CellDataFeatures var4 = new CellDataFeatures(var3, this, var1);
                return (ObservableValue)var2.call(var4);
            }
        }
    }

There’s nothing in this code that checks to see if the return value is a ReadOnlyObjectWrapper (or typed equivalent) and then call getReadOnlyProperty(). It just (effectively) casts the result to ObservableValue<T> and then returns it.

Is this just a mistake in the JavaDocs? Or am I missing something important? Because I’m confused now.

More than anything, I’m at a loss to understand the use case for ReadOnlyObjectWrapper. Any SimpleObjectProperty can be cast to ReadOnlyObjectProperty or ObservableValue just the way that the TableColumn source code does. When would you use ReadOnlyObjectWrapper.getReadOnlyProperty()?????