Casting JComboBox to JTextComponent to get Key Release event
JFrame frame = new JFrame ( "Welcome!!" ); frame . setDefaultCloseOperation ( JFrame . EXIT_ON_CLOSE ); JComboBox cmb = new JComboBox (); cmb . setEditable ( true ); cmb . getEditor (). getEditorComponent (). addKeyListener ( new KeyAdapter () { @Override public void keyReleased ( KeyEvent event ) { if ( event . getKeyChar () == KeyEvent . VK_ENTER ) { if ((( JTextComponent ) (( JComboBox ) (( Component ) event . getSource ()). getParent ()). getEditor () . getEditorComponent ()). getText (). isEmpty ()) System . out . println ( "please dont make me blank" ); } } }); frame . add ( cmb ); frame . setLocationRelativeTo ( null ); frame . setSize ( 300 , 50 ); frame . setVisible ( true );