By Alvin Alexander. Last updated: July 23, 2016
Until a little while ago I don’t think I had ever thought about intentionally casting a null
value in Java, but then I ran into a problem and realized that the solution was to cast a null value, like this:
FileDialog d = new FileDialog((java.awt.Frame) null);
You have to do that in this case because FileDialog
has several one-argument constructors, including one that takes a JFrame
and another that takes a JDialog
. If you just put null
in the constructor the Java compiler or your favorite IDE will complain, so you have to cast the null
value to one of those specific types, and this syntax shows how to do this.
(My app uses multiple frames, and at the moment I’d rather put null
in the FileDialog
constructor than try to determine which frame is currently in the foreground.)