Setting an icon on a JButton

Hello there,

Please review the following code segment....

/*************************************************************/
public class IMIEasternButtonPanel extends JPanel {

private BoxLayout bl = new BoxLayout(this, BoxLayout.LINE_AXIS);
private JButton m_btnUp, m_btnDown;

public IMIEasternButtonPanel(){
setLayout(bl);
setPreferredSize(new Dimension(500,50));
addChilds();
}

public void addChilds(){

boolean b = FilesUtils.isFileExists("up.gif"); //b = true !!!
Icon upIcon = null;
upIcon = new ImageIcon("up.gif");
m_btnUp = new JButton();
m_btnUp.setIcon(upIcon);
m_btnUp.setSize(50, 50);
add(m_btnUp);
/*******************************************************/

Why can't I see the icon on the up button??? Moreover, the button does
not seems to get the correct size as I had set. It is more like a
oblong than a 50X50 square...

Many thanks!

.