Why does the JFrame setSize() method not set the size correctly?

Question

So I\'ve been programming in java for a semester or so, and I\'ve had this problem a few times and finally got around to asking.

If I make a JFrame and

Answer 1

I know that this question is about 6+ years old, but the answer by @Kyle doesn't work.

Using this

setSize(width - (getInsets().left + getInsets().right), height - (getInsets().top + getInsets().bottom));

But this always work in any size:

setSize(width + 14, height + 7);

If you don't want the border to border, and only want the white area, here:

setSize(width + 16, height + 39);

Also this only works on Windows 10, for MacOS users, use @ben's answer.