code: public boolean setReadable(boolean readable, boolean ownerOnly) {
          return doChmod(ownerOnly ? S_IRUSR : (S_IRUSR | S_IRGRP | S_IROTH), readable);
      }
docs: Manipulates the read permissions for the abstract path designated by this
  file.
  
  @param readable
  To allow read permission if true, otherwise disallow
  @param ownerOnly
  To manipulate read permission only for owner if true,
  otherwise for everyone. The manipulation will apply to
  everyone regardless of this value if the underlying system
  does not distinguish owner and other users.
  @return true if and only if the operation succeeded. If the user does not
  have permission to change the access permissions of this abstract
  pathname the operation will fail. If the underlying file system
  does not support read permission and the value of readable is
  false, this operation will fail.
  @since 1.6