FULL PRODUCT VERSION :
java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
In the following code, although JPanel is focusable ( JPanel().isFocusable() == true), I have to call setFocusable() or the focus listener will not be called, why is it so strange ?


class TestJPanel {
 
        public static void main(String[] args){
 
                JFrame frame = new JFrame("test");
                JPanel panel = new JPanel();
 
                System.out.println("JPanel focusable ? " + panel.isFocusable());
 
                // although JPanel is focusable, the below line is necessary
                // or focus listener is not called, why ???
                panel.setFocusable(true);
 
                panel.addFocusListener(new FocusListener() {
 
                        public void focusGained(FocusEvent e) {
                                System.out.println("focusGained " + e);
                        }
 
                        public void focusLost(FocusEvent e) {
                                System.out.println("focusLost " + e);
                        }
                });
 
                frame.add(panel);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
                frame.pack();
                frame.setBounds(100,100,400,300);
                frame.setVisible(true);
        }
}


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
compile the code, run it, click mouse button. the JPanel can get focus only when setFocusable is called.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
If isFocusable() is true, setFocusable(true) need not be called again.
ACTUAL -
setFocusable() must be called for JPanel to gain focus even JPanel.isFocusable() is true

REPRODUCIBILITY :
This bug can be reproduced always.