public class Test implements MouseListener { public static void main (String args[]) { } public void mouseReleased(MouseEvent e) {} public void mouseClicked(MouseEvent e) {} public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mousePressed(MouseEvent e) {} } エラーメッセージ: Test.java:3: Test は abstract でなく、java.awt.event.MouseListener 内の abstract メソッド mouseReleased(java.awt.event.MouseEvent) をオーバーライドしません。