GridFile overwrites not all default methods, what result into errors when using them. So depending on what we can already provide I'll suggest the following implementation:

canRead() // return true
canWrite() // return true
isHidden() // return false
canExecute() // return false
deleteOnExit() // using JVM hooks could be too late and there are no pre-CacheStopped events, ideas welcome
renameTo(File dest) // check if dest is GridFile and rename if its true
setLastModified(long time) // just implement

// for them just throw unsupported operation ATM
getCanonicalPath() // until resolving .. and so on is available
getCanonicalFile() // until resolv path is avail
setReadOnly()
getUsableSpace()
getFreeSpace()
getTotalSpace()
setExecutable(boolean executable)
setExecutable(boolean executable, boolean ownerOnly)
setReadable(boolean readable)
setReadable(boolean readable, boolean ownerOnly)operation
setWritable(boolean writable)
setWritable(boolean writable, boolean ownerOnly)
toURI()
toURL()