build from Oct 10, JDK 1.5

I noticed that when creating a new J2SE project there are many conversions
between URLs and FileObjects called from
FilterClassPathImplementation.createResources(). I see 601 calls through this
call stack

                Called 601 times from:
Lorg/openide/filesystems/FileUtil;.normalizeFile
Lorg/netbeans/modules/masterfs/MasterURLMapper;.getFileObjects
Lorg/openide/filesystems/URLMapper;.findFileObject
Lorg/netbeans/modules/javacore/classpath/MergedClassPathImplementation;.getRoots
Lorg/netbeans/modules/javacore/JMManager;.mergedCPContainsRoot
Lorg/netbeans/modules/javacore/classpath/FilterClassPathImplementation;.createResources

also these calls are very likely related -

                Called 573 times from:
Lorg/openide/filesystems/FileUtil;.normalizeFile
Lorg/netbeans/modules/masterfs/MasterURLMapper;.getFileObjects
Lorg/openide/filesystems/URLMapper;.findFileObject
Lorg/netbeans/core/startup/layers/ArchiveURLMapper;.getFileObjects
Lorg/openide/filesystems/URLMapper;.findFileObject
Lorg/netbeans/modules/javacore/classpath/MergedClassPathImplementation;.getRoots

It seems to me that filtered CP knows about root URLs but converts them to
FileObject and merged CP performs oposite conversion because it keeps list of
URLs. If I got it correctly it might be possible to optimize this. Querying all
the mappers again and again together with normalization of files and accessing
I/O (File.isDirectory calls deeper in call chain) can be avoided then.