JButton btn = new JButton(); btn.setText("Button"); btn.setSize(120,20); btn.setLocation(10, 10); btn.addMouseListener(this); panel.add(btn); @Override public void mouseEntered(MouseEvent e) { // TODO Auto-generated method stub JComponent comp = (JComponent)e.getSource(); comp.setFont(new Font(comp.getFont().getName(), comp.getFont().getStyle(), 40)); }