Different Style object initialization with scala - scala

Question

When I using java there are something like double bracket initialization that actually make some runtime trade off. In scala I discover the simple way to initiate object property like
val button1: Button = new Button
button1.setText("START")
button1.setPrefWidth(100)
Which can be rewriten to
val button2: Button = new Button {
setText("PAUSE")
setPrefWidth(100)
}
Is these make any difference from performance or something else?

Answer 1

The difference is that in the first case you instantiate a new Button object and set its properties to some values (text = "START" and width = 100) and in the second case you create an anonymous class that inherits from Button and initialize its properties in its anonymous initializer (or constructor, not sure - Java's anonymous classes cannot have constructors).
The second case can be roughly rewritten like this (if it weren't an anonymous class):
class MyButton extends Button {
//constructor
setText("START")
setPrefWidth(100)
}
And when you call new MyButton you get an instance of MyButton with text set as "START" and prefWidth set as 100.
If you come from Java background consider this analogy:
Button button = new Button() {
//anonymous initializer
{
setText("START");
setPrefWidth(100);
}
};