这个问题在这里已经有了答案:'MustOverrideaSuperclassMethod'ErrorsafterimportingaprojectintoEclipse(13个答案)关闭5年前。JTextAreamessageDisplayArea=newJTextArea();messageDisplayArea.addMouseListener(newMouseListener(){publicvoidmouseEntered(MouseEventm){JOptionPane.showMessageDialog(null,"a");}});messageDisplayArea.ad