RFR: 8153654: Update jdeps to be multi-release jar aware

[Steve Drach]

The most recent webrev is http://cr.openjdk.java.net/~sdrach/8153654/webrev.11/ <http://cr.openjdk.java.net/~sdrach/8153654/webrev.11/>

Comments inline

>> The latest web revs.  Answers to questions in-line below:
>> 
>> http://cr.openjdk.java.net/~sdrach/8153654/webrev.10/
>> 
>> http://cr.openjdk.java.net/~sdrach/8153654/webrev.jdk/
> 
> This looks pretty good. My main comment is in VersionHelper (see below).
> 
> ClassFileReader.java
> 
> 337                     String[] msg = {"err.multirelease.option.exists", f.getName()};
> 389                             String[] msg = {"err.multirelease.jar.malformed”,
> 390                                     jarfile.getName(), rn
> 391                             };
> 
> `msg` is not used.  These lines can be removed.

Done

> 
> line 81-95: this wants to add to VersionHelper if it’s a versioned entry.  I suggest to move this to VersionHelper, something like this and replace the add method.

I did essentially the same thing, but not exactly the same.

> 
> public static void addIfVersionedEntry(Path jarfile, String realEntryName, String className) {
>    if (realEntryName.startsWith(META_INF_VERSIONS)) {
>        int len = META_INF_VERSIONS.length();
>        int n = realEntryName.indexOf('/', len);
>        if (n > 0) {
>            String version = realEntryName.substring(len, n);
>            assert (Integer.parseInt(version) > 8);
> 
>            String v = versionMap.get(className);
>            if (v != null && !v.equals(version)) {
>                // name associated with a different ClassFile
>                throw new MultiReleaseException("err.multirelease.version.associated", className,
>                    v, version);
>            }
>            versionMap.put(className, version);
>        } else {
>            throw new MultiReleaseException("err.multirelease.jar.malformed",
>                jarfile.toString(), realEntryName);
>        }
>    }
> }
> 
> I prefer to call String::length rather than hardcoding the length.

OK

>  I don’t see why VersionHelper caches ClassFile.  

A JarEntry (base) name has a one to many relationship with versions.  This implies the class name also has a one to many relationship with versions.  But a ClassFile (derived from the contents of the JarEntry) has a one to one relationship with version.  We desire a one to one
relationship for className to version and one way to assure that is to create two maps as I now have done.  I think the code is more obvious  now, at least I hope it is.

> I think it can cache a map from class name to the version for now.  We may have to handle duplicated classes in more than one modular jar (it’s not exported and should be allowed).  We could file a separate issue to look into later.
> 
> This needs a CCC for the new --multi-release option.

That’s next.

> 
> Mandy