void add(InjectableMember member) {
   if (head == null) {
     head = tail = member;
   } else {
     member.previous = tail;
     tail.next = member;
     tail = member;
   }
 }
  /**
   * Returns an ordered, immutable set of injection points for the given type. Members in
   * superclasses come before members in subclasses. Within a class, fields come before methods.
   * Overridden methods are filtered out.
   *
   * @param statics true is this method should return static members, false for instance members
   * @param errors used to record errors
   */
  private static Set<InjectionPoint> getInjectionPoints(
      final TypeLiteral<?> type, boolean statics, Errors errors) {
    InjectableMembers injectableMembers = new InjectableMembers();
    OverrideIndex overrideIndex = null;

    List<TypeLiteral<?>> hierarchy = hierarchyFor(type);
    int topIndex = hierarchy.size() - 1;
    for (int i = topIndex; i >= 0; i--) {
      if (overrideIndex != null && i < topIndex) {
        // Knowing the position within the hierarchy helps us make optimizations.
        if (i == 0) {
          overrideIndex.position = Position.BOTTOM;
        } else {
          overrideIndex.position = Position.MIDDLE;
        }
      }

      TypeLiteral<?> current = hierarchy.get(i);

      for (Field field : current.getRawType().getDeclaredFields()) {
        if (Modifier.isStatic(field.getModifiers()) == statics) {
          Annotation atInject = getAtInject(field);
          if (atInject != null) {
            InjectableField injectableField = new InjectableField(current, field, atInject);
            if (injectableField.jsr330 && Modifier.isFinal(field.getModifiers())) {
              errors.cannotInjectFinalField(field);
            }
            injectableMembers.add(injectableField);
          }
        }
      }

      for (Method method : current.getRawType().getDeclaredMethods()) {
        if (isEligibleForInjection(method, statics)) {
          Annotation atInject = getAtInject(method);
          if (atInject != null) {
            InjectableMethod injectableMethod = new InjectableMethod(current, method, atInject);
            if (checkForMisplacedBindingAnnotations(method, errors)
                || !isValidMethod(injectableMethod, errors)) {
              if (overrideIndex != null) {
                boolean removed =
                    overrideIndex.removeIfOverriddenBy(method, false, injectableMethod);
                if (removed) {
                  logger.log(
                      Level.WARNING,
                      "Method: {0} is not a valid injectable method ("
                          + "because it either has misplaced binding annotations "
                          + "or specifies type parameters) but is overriding a method that is valid. "
                          + "Because it is not valid, the method will not be injected. "
                          + "To fix this, make the method a valid injectable method.",
                      method);
                }
              }
              continue;
            }
            if (statics) {
              injectableMembers.add(injectableMethod);
            } else {
              if (overrideIndex == null) {
                /*
                 * Creating the override index lazily means that the first type in the hierarchy
                 * with injectable methods (not necessarily the top most type) will be treated as
                 * the TOP position and will enjoy the same optimizations (no checks for overridden
                 * methods, etc.).
                 */
                overrideIndex = new OverrideIndex(injectableMembers);
              } else {
                // Forcibly remove the overriden method, otherwise we'll inject
                // it twice.
                overrideIndex.removeIfOverriddenBy(method, true, injectableMethod);
              }
              overrideIndex.add(injectableMethod);
            }
          } else {
            if (overrideIndex != null) {
              boolean removed = overrideIndex.removeIfOverriddenBy(method, false, null);
              if (removed) {
                logger.log(
                    Level.WARNING,
                    "Method: {0} is not annotated with @Inject but "
                        + "is overriding a method that is annotated with @javax.inject.Inject.  Because "
                        + "it is not annotated with @Inject, the method will not be injected. "
                        + "To fix this, annotate the method with @Inject.",
                    method);
              }
            }
          }
        }
      }
    }

    if (injectableMembers.isEmpty()) {
      return Collections.emptySet();
    }

    ImmutableSet.Builder<InjectionPoint> builder = ImmutableSet.builder();
    for (InjectableMember im = injectableMembers.head; im != null; im = im.next) {
      try {
        builder.add(im.toInjectionPoint());
      } catch (ConfigurationException ignorable) {
        if (!im.optional) {
          errors.merge(ignorable.getErrorMessages());
        }
      }
    }
    return builder.build();
  }