一个理解面向对象很好的例子

package sys; import org.apache.log4j.Logger; import user.Admin; import user.Employee; import user.User; public class ControlSys { private Door door = new Door(); private Computer computer = new Computer(); private InputDevice inputDevice = new InputDevice(); private Admin admin; private Logger logger = Logger.getLogger(ControlSys.class); public ControlSys(Admin admin) { this.admin = admin; log("门禁系统启动"); } //输入 public void input(Employee user) { log("员工（" + user.getName() + "）使用输入设备"); String input = inputDevice.getInput(); boolean checked = computer.check(input); if (checked) { log("员工（" + user.getName() + "）通过身份验证"); useDoor(); } else { log("员工（" + user.getName() + "）身份验证失败"); } } //门铃 public void ring(User user) { log("客人（" + user.getName() + "）来访"); boolean allowed = admin.allowRing(user); if (allowed) { log("管理员（" + admin.getName() + "）允许来客通过"); useDoor(); } else { log("管理员（" + admin.getName() + "）拒绝开门"); } } // public void addValidData(String validData) { try { computer.addData( validData ); log("管理员（"+admin.getName()+"）添加了新的验证数据"); } catch (Exception e) { processException(e); } } //使用门(开,5秒后关) private void useDoor() { door.open(); try { Thread.sleep(5000); } catch (InterruptedException e) { processException( e ); } finally { door.close(); } } //记录日志 private void log(String message) { logger.info(message); } //处理异常 private void processException(Exception e) { logger.error(e); e.printStackTrace(); } }