Because Java does not understand Processing commands. You can try to import processing.core, or try to convert millis() to Java. Or, rename it to .PDE.

I didn't realize that eclipse understood *.pde files.  Is this part of the Processing Plugin for Eclipse?

Code in .pde files is actually internal to the main class extending PApplet. It has access to the "functions" of Processing, which are actually methods of your class (named after your sketch).
By design, code in .java files is put in separate classes, which you have to declare yourself. To access the methods of PApplet, you need a reference to an object of this type. Which is usually done, eg. in libraries, by passing this as parameter to the constructor of your class. This parameter is stored in a field (a class variable), say pa, and is used in the class like: pa.millis(), pa.line( ... ) and so on.