org.argeo.osgi.boot/src/org/argeo/osgi/boot/internal/springutil/CollectionUtils.java

   1 /*
   2  * Copyright 2002-2008 the original author or authors.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 package org.argeo.osgi.boot.internal.springutil;
  18
  19 import java.util.Arrays;
  20 import java.util.Collection;
  21 import java.util.Enumeration;
  22 import java.util.Iterator;
  23 import java.util.List;
  24 import java.util.Map;
  25 import java.util.Properties;
  26
  27 /**
  28  * Miscellaneous collection utility methods.
  29  * Mainly for internal use within the framework.
  30  *
  31  * @author Juergen Hoeller
  32  * @author Rob Harrop
  33  * @since 1.1.3
  34  */
  35 @SuppressWarnings({ "rawtypes", "unchecked" })
  36 public abstract class CollectionUtils {
  37
  38         /**
  39          * Return <code>true</code> if the supplied Collection is <code>null</code>
  40          * or empty. Otherwise, return <code>false</code>.
  41          * @param collection the Collection to check
  42          * @return whether the given Collection is empty
  43          */
  44         public static boolean isEmpty(Collection collection) {
  45                 return (collection == null || collection.isEmpty());
  46         }
  47
  48         /**
  49          * Return <code>true</code> if the supplied Map is <code>null</code>
  50          * or empty. Otherwise, return <code>false</code>.
  51          * @param map the Map to check
  52          * @return whether the given Map is empty
  53          */
  54         public static boolean isEmpty(Map map) {
  55                 return (map == null || map.isEmpty());
  56         }
  57
  58         /**
  59          * Convert the supplied array into a List. A primitive array gets
  60          * converted into a List of the appropriate wrapper type.
  61          * <p>A <code>null</code> source value will be converted to an
  62          * empty List.
  63          * @param source the (potentially primitive) array
  64          * @return the converted List result
  65          * @see ObjectUtils#toObjectArray(Object)
  66          */
  67         public static List arrayToList(Object source) {
  68                 return Arrays.asList(ObjectUtils.toObjectArray(source));
  69         }
  70
  71         /**
  72          * Merge the given array into the given Collection.
  73          * @param array the array to merge (may be <code>null</code>)
  74          * @param collection the target Collection to merge the array into
  75          */
  76         public static void mergeArrayIntoCollection(Object array, Collection collection) {
  77                 if (collection == null) {
  78                         throw new IllegalArgumentException("Collection must not be null");
  79                 }
  80                 Object[] arr = ObjectUtils.toObjectArray(array);
  81                 for (int i = 0; i < arr.length; i++) {
  82                         collection.add(arr[i]);
  83                 }
  84         }
  85
  86         /**
  87          * Merge the given Properties instance into the given Map,
  88          * copying all properties (key-value pairs) over.
  89          * <p>Uses <code>Properties.propertyNames()</code> to even catch
  90          * default properties linked into the original Properties instance.
  91          * @param props the Properties instance to merge (may be <code>null</code>)
  92          * @param map the target Map to merge the properties into
  93          */
  94         public static void mergePropertiesIntoMap(Properties props, Map map) {
  95                 if (map == null) {
  96                         throw new IllegalArgumentException("Map must not be null");
  97                 }
  98                 if (props != null) {
  99                         for (Enumeration en = props.propertyNames(); en.hasMoreElements();) {
 100                                 String key = (String) en.nextElement();
 101                                 map.put(key, props.getProperty(key));
 102                         }
 103                 }
 104         }
 105
 106
 107         /**
 108          * Check whether the given Iterator contains the given element.
 109          * @param iterator the Iterator to check
 110          * @param element the element to look for
 111          * @return <code>true</code> if found, <code>false</code> else
 112          */
 113         public static boolean contains(Iterator iterator, Object element) {
 114                 if (iterator != null) {
 115                         while (iterator.hasNext()) {
 116                                 Object candidate = iterator.next();
 117                                 if (ObjectUtils.nullSafeEquals(candidate, element)) {
 118                                         return true;
 119                                 }
 120                         }
 121                 }
 122                 return false;
 123         }
 124
 125         /**
 126          * Check whether the given Enumeration contains the given element.
 127          * @param enumeration the Enumeration to check
 128          * @param element the element to look for
 129          * @return <code>true</code> if found, <code>false</code> else
 130          */
 131         public static boolean contains(Enumeration enumeration, Object element) {
 132                 if (enumeration != null) {
 133                         while (enumeration.hasMoreElements()) {
 134                                 Object candidate = enumeration.nextElement();
 135                                 if (ObjectUtils.nullSafeEquals(candidate, element)) {
 136                                         return true;
 137                                 }
 138                         }
 139                 }
 140                 return false;
 141         }
 142
 143         /**
 144          * Check whether the given Collection contains the given element instance.
 145          * <p>Enforces the given instance to be present, rather than returning
 146          * <code>true</code> for an equal element as well.
 147          * @param collection the Collection to check
 148          * @param element the element to look for
 149          * @return <code>true</code> if found, <code>false</code> else
 150          */
 151         public static boolean containsInstance(Collection collection, Object element) {
 152                 if (collection != null) {
 153                         for (Iterator it = collection.iterator(); it.hasNext();) {
 154                                 Object candidate = it.next();
 155                                 if (candidate == element) {
 156                                         return true;
 157                                 }
 158                         }
 159                 }
 160                 return false;
 161         }
 162
 163         /**
 164          * Return <code>true</code> if any element in '<code>candidates</code>' is
 165          * contained in '<code>source</code>'; otherwise returns <code>false</code>.
 166          * @param source the source Collection
 167          * @param candidates the candidates to search for
 168          * @return whether any of the candidates has been found
 169          */
 170         public static boolean containsAny(Collection source, Collection candidates) {
 171                 if (isEmpty(source) || isEmpty(candidates)) {
 172                         return false;
 173                 }
 174                 for (Iterator it = candidates.iterator(); it.hasNext();) {
 175                         if (source.contains(it.next())) {
 176                                 return true;
 177                         }
 178                 }
 179                 return false;
 180         }
 181
 182         /**
 183          * Return the first element in '<code>candidates</code>' that is contained in
 184          * '<code>source</code>'. If no element in '<code>candidates</code>' is present in
 185          * '<code>source</code>' returns <code>null</code>. Iteration order is
 186          * {@link Collection} implementation specific.
 187          * @param source the source Collection
 188          * @param candidates the candidates to search for
 189          * @return the first present object, or <code>null</code> if not found
 190          */
 191         public static Object findFirstMatch(Collection source, Collection candidates) {
 192                 if (isEmpty(source) || isEmpty(candidates)) {
 193                         return null;
 194                 }
 195                 for (Iterator it = candidates.iterator(); it.hasNext();) {
 196                         Object candidate = it.next();
 197                         if (source.contains(candidate)) {
 198                                 return candidate;
 199                         }
 200                 }
 201                 return null;
 202         }
 203
 204         /**
 205          * Find a single value of the given type in the given Collection.
 206          * @param collection the Collection to search
 207          * @param type the type to look for
 208          * @return a value of the given type found if there is a clear match,
 209          * or <code>null</code> if none or more than one such value found
 210          */
 211         public static Object findValueOfType(Collection collection, Class type) {
 212                 if (isEmpty(collection)) {
 213                         return null;
 214                 }
 215                 Object value = null;
 216                 for (Iterator it = collection.iterator(); it.hasNext();) {
 217                         Object obj = it.next();
 218                         if (type == null || type.isInstance(obj)) {
 219                                 if (value != null) {
 220                                         // More than one value found... no clear single value.
 221                                         return null;
 222                                 }
 223                                 value = obj;
 224                         }
 225                 }
 226                 return value;
 227         }
 228
 229         /**
 230          * Find a single value of one of the given types in the given Collection:
 231          * searching the Collection for a value of the first type, then
 232          * searching for a value of the second type, etc.
 233          * @param collection the collection to search
 234          * @param types the types to look for, in prioritized order
 235          * @return a value of one of the given types found if there is a clear match,
 236          * or <code>null</code> if none or more than one such value found
 237          */
 238         public static Object findValueOfType(Collection collection, Class[] types) {
 239                 if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
 240                         return null;
 241                 }
 242                 for (int i = 0; i < types.length; i++) {
 243                         Object value = findValueOfType(collection, types[i]);
 244                         if (value != null) {
 245                                 return value;
 246                         }
 247                 }
 248                 return null;
 249         }
 250
 251         /**
 252          * Determine whether the given Collection only contains a single unique object.
 253          * @param collection the Collection to check
 254          * @return <code>true</code> if the collection contains a single reference or
 255          * multiple references to the same instance, <code>false</code> else
 256          */
 257         public static boolean hasUniqueObject(Collection collection) {
 258                 if (isEmpty(collection)) {
 259                         return false;
 260                 }
 261                 boolean hasCandidate = false;
 262                 Object candidate = null;
 263                 for (Iterator it = collection.iterator(); it.hasNext();) {
 264                         Object elem = it.next();
 265                         if (!hasCandidate) {
 266                                 hasCandidate = true;
 267                                 candidate = elem;
 268                         }
 269                         else if (candidate != elem) {
 270                                 return false;
 271                         }
 272                 }
 273                 return true;
 274         }
 275
 276 }