question: public void add ( Permission permission ) { if ( ! ( permission instanceof FilePermission ) ) throw new IllegalArgumentException ( "invalid permission: " + permission ) ; if ( isReadOnly ( ) ) throw new SecurityException ( "attempt to add a Permission to a readonly PermissionCollection" ) ; synchronized ( this ) { perms . add ( permission ) ; } }
target:  Adds a permission to the FilePermissionCollection. The key for the hash is permission.path.