Question

I want to re-use a Builder instance to create several controls but I’m getting compile errors which I don’t understand. I think they’re caused by me not understanding generics properly. Can anyone help?

ButtonBuilder builder = ButtonBuilder.create().minHeight(40.0).minWidth(40.0);
Button button1 = builder.onAction(clickHandler).build(); // Error
Button button2 = ButtonBuilder.create().minHeight(40.0).minWidth(40.0).onAction(clickHandler).build(); //OK

where clickHandler is a EventHandler<ActionEvent>

The error I get is

error: cannot find symbol
    Button button1 = builder.onAction(clickHandler).build();
                                                   ^
symbol:   method build()
location: class ButtonBaseBuilder

ButtonBaseBuilder implements Builder so it should have a build() method, shouldn’t it? Also if I run everything together (as in button2) it is OK.

This is on JDK 7.0u4 and JavaFX SDK 2.1

Thanks in advance,
Pete

Answer 1

You need to pass ButtonBuilder generic parameter to use builders that way:

    ButtonBuilder<? extends ButtonBuilder> builder =
                     ButtonBuilder.create().minHeight(40.0).minWidth(40.0);
    Button button1 = builder.onAction(clickHandler).build();