true if the supplied Collection is null
- * or empty. Otherwise, return false.
- * @param collection the Collection to check
- * @return whether the given Collection is empty
- */
- public static boolean isEmpty(Collection collection) {
- return (collection == null || collection.isEmpty());
- }
-
- /**
- * Return true if the supplied Map is null
- * or empty. Otherwise, return false.
- * @param map the Map to check
- * @return whether the given Map is empty
- */
- public static boolean isEmpty(Map map) {
- return (map == null || map.isEmpty());
- }
-
- /**
- * Convert the supplied array into a List. A primitive array gets
- * converted into a List of the appropriate wrapper type.
- * A null source value will be converted to an
- * empty List.
- * @param source the (potentially primitive) array
- * @return the converted List result
- * @see ObjectUtils#toObjectArray(Object)
- */
- public static List arrayToList(Object source) {
- return Arrays.asList(ObjectUtils.toObjectArray(source));
- }
-
- /**
- * Merge the given array into the given Collection.
- * @param array the array to merge (may be null)
- * @param collection the target Collection to merge the array into
- */
- public static void mergeArrayIntoCollection(Object array, Collection collection) {
- if (collection == null) {
- throw new IllegalArgumentException("Collection must not be null");
- }
- Object[] arr = ObjectUtils.toObjectArray(array);
- for (int i = 0; i < arr.length; i++) {
- collection.add(arr[i]);
- }
- }
-
- /**
- * Merge the given Properties instance into the given Map,
- * copying all properties (key-value pairs) over.
- *
Uses Properties.propertyNames() to even catch
- * default properties linked into the original Properties instance.
- * @param props the Properties instance to merge (may be null)
- * @param map the target Map to merge the properties into
- */
- public static void mergePropertiesIntoMap(Properties props, Map map) {
- if (map == null) {
- throw new IllegalArgumentException("Map must not be null");
- }
- if (props != null) {
- for (Enumeration en = props.propertyNames(); en.hasMoreElements();) {
- String key = (String) en.nextElement();
- map.put(key, props.getProperty(key));
- }
- }
- }
-
-
- /**
- * Check whether the given Iterator contains the given element.
- * @param iterator the Iterator to check
- * @param element the element to look for
- * @return true if found, false else
- */
- public static boolean contains(Iterator iterator, Object element) {
- if (iterator != null) {
- while (iterator.hasNext()) {
- Object candidate = iterator.next();
- if (ObjectUtils.nullSafeEquals(candidate, element)) {
- return true;
- }
- }
- }
- return false;
- }
-
- /**
- * Check whether the given Enumeration contains the given element.
- * @param enumeration the Enumeration to check
- * @param element the element to look for
- * @return true if found, false else
- */
- public static boolean contains(Enumeration enumeration, Object element) {
- if (enumeration != null) {
- while (enumeration.hasMoreElements()) {
- Object candidate = enumeration.nextElement();
- if (ObjectUtils.nullSafeEquals(candidate, element)) {
- return true;
- }
- }
- }
- return false;
- }
-
- /**
- * Check whether the given Collection contains the given element instance.
- *
Enforces the given instance to be present, rather than returning
- * true for an equal element as well.
- * @param collection the Collection to check
- * @param element the element to look for
- * @return true if found, false else
- */
- public static boolean containsInstance(Collection collection, Object element) {
- if (collection != null) {
- for (Iterator it = collection.iterator(); it.hasNext();) {
- Object candidate = it.next();
- if (candidate == element) {
- return true;
- }
- }
- }
- return false;
- }
-
- /**
- * Return true if any element in 'candidates' is
- * contained in 'source'; otherwise returns false.
- * @param source the source Collection
- * @param candidates the candidates to search for
- * @return whether any of the candidates has been found
- */
- public static boolean containsAny(Collection source, Collection candidates) {
- if (isEmpty(source) || isEmpty(candidates)) {
- return false;
- }
- for (Iterator it = candidates.iterator(); it.hasNext();) {
- if (source.contains(it.next())) {
- return true;
- }
- }
- return false;
- }
-
- /**
- * Return the first element in 'candidates' that is contained in
- * 'source'. If no element in 'candidates' is present in
- * 'source' returns null. Iteration order is
- * {@link Collection} implementation specific.
- * @param source the source Collection
- * @param candidates the candidates to search for
- * @return the first present object, or null if not found
- */
- public static Object findFirstMatch(Collection source, Collection candidates) {
- if (isEmpty(source) || isEmpty(candidates)) {
- return null;
- }
- for (Iterator it = candidates.iterator(); it.hasNext();) {
- Object candidate = it.next();
- if (source.contains(candidate)) {
- return candidate;
- }
- }
- return null;
- }
-
- /**
- * Find a single value of the given type in the given Collection.
- * @param collection the Collection to search
- * @param type the type to look for
- * @return a value of the given type found if there is a clear match,
- * or null if none or more than one such value found
- */
- public static Object findValueOfType(Collection collection, Class type) {
- if (isEmpty(collection)) {
- return null;
- }
- Object value = null;
- for (Iterator it = collection.iterator(); it.hasNext();) {
- Object obj = it.next();
- if (type == null || type.isInstance(obj)) {
- if (value != null) {
- // More than one value found... no clear single value.
- return null;
- }
- value = obj;
- }
- }
- return value;
- }
-
- /**
- * Find a single value of one of the given types in the given Collection:
- * searching the Collection for a value of the first type, then
- * searching for a value of the second type, etc.
- * @param collection the collection to search
- * @param types the types to look for, in prioritized order
- * @return a value of one of the given types found if there is a clear match,
- * or null if none or more than one such value found
- */
- public static Object findValueOfType(Collection collection, Class[] types) {
- if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
- return null;
- }
- for (int i = 0; i < types.length; i++) {
- Object value = findValueOfType(collection, types[i]);
- if (value != null) {
- return value;
- }
- }
- return null;
- }
-
- /**
- * Determine whether the given Collection only contains a single unique object.
- * @param collection the Collection to check
- * @return true if the collection contains a single reference or
- * multiple references to the same instance, false else
- */
- public static boolean hasUniqueObject(Collection collection) {
- if (isEmpty(collection)) {
- return false;
- }
- boolean hasCandidate = false;
- Object candidate = null;
- for (Iterator it = collection.iterator(); it.hasNext();) {
- Object elem = it.next();
- if (!hasCandidate) {
- hasCandidate = true;
- candidate = elem;
- }
- else if (candidate != elem) {
- return false;
- }
- }
- return true;
- }
-
-}