When an element of the classpath points to a directory that does not exist,
a message does not appear until looking for a path on that classpath.
It would be helpful if a warning was output for that initial error,
to more easily detect the problem.

Given -classpath a:b, at first look, the warning might be something like:

  warning - path "b" does not exist

(If it's possible for whitespace to be interpreted as a path,
quotes around the path name, as shown, would help.)

In the case that prompted this feature request, when a jar file is
under a home directory, non-leading tildes (that represent the
home directory) are not expanded (nor should they be) in -classpath
or -sourcepath arguments. Currently, a "Package xxx not found in import"
error is thrown when trying to load a package from that path.
In the following example, the above message would
help narrow the problem, but not completely resolve it
for the user:

  warning - path "~/java/classes/jh.jar" does not exist

Because the user is unaware that the shell interprets the
first tilde but not following ones, he is still left wondering
where the trick lies, as "ls ~/java/classes/jh.jar"
indicates the file exists. Perhaps the message can
be worded more carefully to make this distinction to the
user, such as:

  warning - path "~/java/classes/jh.jar" does not exist (~ does not expand)

Or perhaps for Unix, check for leading "~/" and warn to replace
it with the expanded path?

Due to the tricky nature of the problem, this bug was quite
time-consuming to narrow down and fix -- it would seem to warrant
an extra care in the warning message.


Example:

The jar files exist:

% ls ~/java/classes/xerces.jar ~/java/classes/jh.jar
/nethome/qwang/java/classes/jh.jar
/nethome/qwang/java/classes/xerces.jar

However, when using a tilde in the second element (/java/classes/jh.jar),
packages inside that jar file cannot be found:

% javadoc -d ~/java/src/doc3 -classpath ~/java/classes/xerces.jar:~/java/classes/jh.jar -sourcepath ~/java/src pipe
    Loading source files for package pipe...
    Constructing Javadoc information... /nethome/qwang/java/src/pipe/form/PipeMenu.java:14: Package javax.help not found in import.
                        import javax.help.*;
                        ^

However, it works when "/nethome/qwang" is used instead of tilde.
(Putting quotes around the classpath argument does not work)

..............

NOTE: The above example is abbreviated from the original bug reported
in length at the Javadoc forum, "Package not found in import" at:
http://forum.java.sun.com/thread.jsp?forum=41&thread=241106

This is a follow-on to bug 4668475:
"Package not found" error when tilde (~) is used as second path in -classpath