When using Eclipse straight out of the box, if you click on a Java-provided class, like the
FileWriter class, you won't get much help when the Eclipse Class File Editor is shown. All you'll see is some binary information, with these messages at the top of the file:
Source not found
The jar file classes.jar has no source attachment.
You can attach the source by clicking the Attach Source below:
(The message really should end with "by clicking the Attach Source button below:")