Loopy is a Java API for accessing various file systems in a read-only manner. Loopy was developed as a plug-in for Apache Commons VFS. Currently, it only supports the ISO9660 file system (i.e. .iso files).
To use loopy with VFS, simply include the jar on the classpath and access your iso file using the following URL format: iso:/path/to/file.iso.
Loopy is hosted at Sourceforge. You can download the latest version here.