error codes are values that identify different types of errors in the Windows API. Most functions do not report the error code directly; instead, they simply return a flag specifying if some error occured or not.
a compatibility layer for running Windows programs. Wine does not require Microsoft Windows, as it is a completely free alternative implementation of the Windows API consisting of 100% non-Microsoft code, however Wine can optionally use native Windows DLL
discuss how paintComponent can be overridden to customize the look of your components, and then we'll discuss a trick that uses paintChildren to paint custom content on top of the component and its children.