code: private static Set<ObjectPermission> getPermissions(Collection<String> identifiers) {
  
          // Include one READ permission for each of the given identifiers
          Set<ObjectPermission> permissions = new HashSet<ObjectPermission>();
          for (String identifier : identifiers)
              permissions.add(new ObjectPermission(ObjectPermission.Type.READ, identifier));
  
          return permissions;
  
      }
  
      /**
       * Creates a new SharedObjectPermissionSet which grants read-only access to
       * the objects having the given identifiers. No other permissions are
       * granted.
       *
       * @param identifiers
       *     The identifiers of the objects for which READ access should be
       *     granted.
       */
      public SharedObjectPermissionSet(Collection<String> identifiers) {
          super(getPermissions(identifiers));
      }
  
  }
docs: Returns a new Set of ObjectPermissions defining READ access for each of
  the given identifiers.
  
  @param identifiers
  The identifiers of the objects for which READ permission should be
  granted.
  
  @return
  A new Set of ObjectPermissions granting READ access for each of the
  given identifiers.