+
+ /**
+ * Check whether specified Map is null and if so return an immutable map instead. This method supports
+ * non-null default getter methods.
+ *
+ * @param <K> key type
+ * @param <V> value type
+ * @param input input map, may be null
+ * @return Input map or an empty map.
+ */
+ public static <K, V> @NonNull Map<K, V> nonnull(final @Nullable Map<K, V> input) {
+ return input != null ? input : ImmutableMap.of();
+ }
+
+ /**
+ * Check whether specified List is empty and if so return null, otherwise return input list. This method supports
+ * Builder/implementation list handover.
+ *
+ * @param <T> list element type
+ * @param input input list, may be null
+ * @return Input list or null.
+ */
+ public static <T> @Nullable List<T> emptyToNull(final @Nullable List<T> input) {
+ return input != null && input.isEmpty() ? null : input;
+ }
+
+ /**
+ * Check whether specified Map is empty and if so return null, otherwise return input map. This method supports
+ * Builder/implementation list handover.
+ *
+ * @param <K> key type
+ * @param <V> value type
+ * @param input input map, may be null
+ * @return Input map or null.
+ */
+ public static <K, V> @Nullable Map<K, V> emptyToNull(final @Nullable Map<K, V> input) {
+ return input != null && input.isEmpty() ? null : input;
+ }
+
+ /**
+ * Return hash code of a single-property wrapper class. Since the wrapper is not null, we really want to discern
+ * this object being present, hence {@link Objects#hashCode()} is not really useful we would end up with {@code 0}
+ * for both non-present and present-with-null objects.
+ *
+ * @param obj Internal object to hash
+ * @return Wrapper object hash code
+ */
+ public static int wrapperHashCode(final @Nullable Object obj) {
+ return wrapHashCode(Objects.hashCode(obj));
+ }
+
+ /**
+ * Return hash code of a single-property wrapper class. Since the wrapper is not null, we really want to discern
+ * this object being present, hence {@link Arrays#hashCode()} is not really useful we would end up with {@code 0}
+ * for both non-present and present-with-null objects.
+ *
+ * @param obj Internal object to hash
+ * @return Wrapper object hash code
+ */
+ public static int wrapperHashCode(final byte @Nullable[] obj) {
+ return wrapHashCode(Arrays.hashCode(obj));
+ }
+
+ /**
+ * Utility method for checking whether a target object is a compatible DataObject.
+ *
+ * @param requiredClass Required DataObject class
+ * @param obj Object to check, may be null
+ * @return Object cast to required class, if its implemented class matches requirement, null otherwise
+ * @throws NullPointerException if {@code requiredClass} is null
+ */
+ public static <T extends DataObject> @Nullable T checkCast(final @NonNull Class<T> requiredClass,
+ final @Nullable Object obj) {
+ return obj instanceof DataObject && requiredClass.equals(((DataObject) obj).implementedInterface())
+ ? requiredClass.cast(obj) : null;
+ }
+
+ /**
+ * Utility method for checking whether a target object is compatible.
+ *
+ * @param requiredClass Required class
+ * @param fieldName name of the field being filled
+ * @param obj Object to check, may be null
+ * @return Object cast to required class, if its class matches requirement, or null
+ * @throws IllegalArgumentException if {@code obj} is not an instance of {@code requiredClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ public static <T> @Nullable T checkFieldCast(final @NonNull Class<T> requiredClass, final @NonNull String fieldName,
+ final @Nullable Object obj) {
+ try {
+ return requiredClass.cast(obj);
+ } catch (ClassCastException e) {
+ throw new IllegalArgumentException("Invalid input value for property \"" + fieldName + "\"", e);
+ }
+ }
+
+ /**
+ * Utility method for checking whether a target object is compatible with a particular identity class.
+ *
+ * @param requiredClass Required class
+ * @param fieldName name of the field being filled
+ * @param obj Object to check, may be null
+ * @return Object cast to required class, if it class matches requirement, or null
+ * @throws IllegalArgumentException if {@code obj} is not an Class representing {@code requiredClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ public static <T extends BaseIdentity> @Nullable Class<? extends T> checkFieldCastIdentity(
+ final @NonNull Class<T> requiredClass, final @NonNull String fieldName, final @Nullable Object obj) {
+ if (obj == null) {
+ return null;
+ }
+ checkArgument(obj instanceof Class, "Invalid input value \"%s\" for property \"%s\"", obj, fieldName);
+
+ try {
+ return ((Class<?>) obj).asSubclass(requiredClass);
+ } catch (ClassCastException e) {
+ throw new IllegalArgumentException("Invalid input value \"" + obj + "\" for property \"" + fieldName + "\"",
+ e);
+ }
+ }
+
+ /**
+ * Utility method for checking whether the items of target list is compatible.
+ *
+ * @param requiredClass Required item class
+ * @param fieldName name of the field being filled
+ * @param list List, which items should be checked
+ * @return Type-checked List
+ * @throws IllegalArgumentException if a list item is not instance of {@code requiredClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> @Nullable List<T> checkListFieldCast(final @NonNull Class<?> requiredClass,
+ final @NonNull String fieldName, final @Nullable List<?> list) {
+ checkCollectionField(requiredClass, fieldName, list);
+ return (List<T>) list;
+ }
+
+ /**
+ * Utility method for checking whether the items of a target list are compatible with a particular identity class.
+ *
+ * @param requiredClass Required class
+ * @param fieldName name of the field being filled
+ * @param list List, which items should be checked
+ * @return Type-checked List
+ * @throws IllegalArgumentException if a list item is not a Class representing {@code requiredClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ @SuppressWarnings("unchecked")
+ public static <T extends BaseIdentity> @Nullable List<Class<? extends T>> checkListFieldCastIdentity(
+ final @NonNull Class<T> requiredClass, final @NonNull String fieldName, final @Nullable List<?> list) {
+ checkCollectionFieldIdentity(requiredClass, fieldName, list);
+ return (List<Class<? extends T>>) list;
+ }
+
+ /**
+ * Utility method for checking whether the items of target set is compatible.
+ *
+ * @param requiredClass Required item class
+ * @param fieldName name of the field being filled
+ * @param set Set, which items should be checked
+ * @return Type-checked Set
+ * @throws IllegalArgumentException if a set item is not instance of {@code requiredItemClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> @Nullable Set<T> checkSetFieldCast(final @NonNull Class<?> requiredClass,
+ final @NonNull String fieldName, final @Nullable Set<?> set) {
+ checkCollectionField(requiredClass, fieldName, set);
+ return (Set<T>) set;
+ }
+
+ /**
+ * Utility method for checking whether the items of a target set are compatible with a particular identity class.
+ *
+ * @param requiredClass Required class
+ * @param fieldName name of the field being filled
+ * @param set Set, which items should be checked
+ * @return Type-checked Set
+ * @throws IllegalArgumentException if a set item is not a Class representing {@code requiredClass}
+ * @throws NullPointerException if {@code requiredClass} or {@code fieldName} is null
+ */
+ @SuppressWarnings("unchecked")
+ public static <T extends BaseIdentity> @Nullable Set<Class<? extends T>> checkSetFieldCastIdentity(
+ final @NonNull Class<T> requiredClass, final @NonNull String fieldName, final @Nullable Set<?> set) {
+ checkCollectionFieldIdentity(requiredClass, fieldName, set);
+ return (Set<Class<? extends T>>) set;
+ }
+
+ @SuppressFBWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+ justification = "Internal NPE->IAE conversion")
+ private static void checkCollectionField(final @NonNull Class<?> requiredClass,
+ final @NonNull String fieldName, final @Nullable Collection<?> collection) {
+ if (collection != null) {
+ try {
+ collection.forEach(item -> requiredClass.cast(requireNonNull(item)));
+ } catch (ClassCastException | NullPointerException e) {
+ throw new IllegalArgumentException("Invalid input item for property \"" + requireNonNull(fieldName)
+ + "\"", e);
+ }
+ }
+ }
+
+ @SuppressFBWarnings(value = "DCN_NULLPOINTER_EXCEPTION",
+ justification = "Internal NPE->IAE conversion")
+ private static void checkCollectionFieldIdentity(final @NonNull Class<?> requiredClass,
+ final @NonNull String fieldName, final @Nullable Collection<?> collection) {
+ if (collection != null) {
+ try {
+ collection.forEach(item -> ((Class<?>) item).asSubclass(requiredClass));
+ } catch (ClassCastException | NullPointerException e) {
+ throw new IllegalArgumentException("Invalid input item for property \"" + requireNonNull(fieldName)
+ + "\"", e);
+ }
+ }
+ }
+
+ /**
+ * The constant '31' is the result of folding this code:
+ * <pre>
+ * <code>
+ * final int prime = 31;
+ * int result = 1;
+ * result = result * prime + Objects.hashCode(obj);
+ * return result;
+ * </code>
+ * </pre>
+ * when hashCode is returned as 0, such as due to obj being null or its hashCode being 0.
+ *
+ * @param hash Wrapped object hash
+ * @return Wrapper object hash
+ */
+ private static int wrapHashCode(final int hash) {
+ return hash == 0 ? 31 : hash;
+ }