ADDITIONAL SYSTEM INFORMATION :
Operating System: Microsoft Windows [Version 10.0.16299.371] (Windows 10 with 1709)
Java: Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)
java: Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.1+10, mixed mode)


A DESCRIPTION OF THE PROBLEM :
The following demo source gives different JFrame size and title height from that on Java 8, if JFrame.setResizable(false) is not called frame size on Java 9/10 is same as that on Java 8.

This problem can be repeated with both Java 9.0.4 and Java 10.0.1 (download from Oracle).

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Java 8 / Java 9 / Java 10 gives same appearance.
ACTUAL -
Java 9 / Java 10 gives different frame size and title height from Java 8.

---------- BEGIN SOURCE ----------
public class FirstFrame extends JFrame
{
public FirstFrame()
{
JToolBar statusbar = new JToolBar();

statusbar.add(new JLabel("Status:"));
getContentPane().add(statusbar, BorderLayout.SOUTH);

setSize(new Dimension(300, 300));
setResizable(false); // problem comes here.

super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
super.setVisible(true);
}

public static void main(String[] args) throws Exception
{
new FirstFrame();
}
}
---------- END SOURCE ----------

FREQUENCY : always