scheduler class的用法和樣例：
例句
- The plug-in utility class would listen for events from this button.
插件實用程序類將偵聽來自這個按鈕的事件。 - Our application class instantiates the Frame object we just designed, renders it to the screen, and sets it as the top-most window of our application.
我們的應用程序類實例化了一個剛才設計的框架對象，把它繪製在屏幕上，並設置成程序的頂層窗口。
