001 //$HeadURL: svn+ssh://jwilden@svn.wald.intevation.org/deegree/base/branches/2.5_testing/src/org/deegree/framework/util/CollectionUtils.java $
002 /*----------------------------------------------------------------------------
003 This file is part of deegree, http://deegree.org/
004 Copyright (C) 2001-2009 by:
005 Department of Geography, University of Bonn
006 and
007 lat/lon GmbH
008
009 This library is free software; you can redistribute it and/or modify it under
010 the terms of the GNU Lesser General Public License as published by the Free
011 Software Foundation; either version 2.1 of the License, or (at your option)
012 any later version.
013 This library is distributed in the hope that it will be useful, but WITHOUT
014 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
015 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
016 details.
017 You should have received a copy of the GNU Lesser General Public License
018 along with this library; if not, write to the Free Software Foundation, Inc.,
019 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
020
021 Contact information:
022
023 lat/lon GmbH
024 Aennchenstr. 19, 53177 Bonn
025 Germany
026 http://lat-lon.de/
027
028 Department of Geography, University of Bonn
029 Prof. Dr. Klaus Greve
030 Postfach 1147, 53001 Bonn
031 Germany
032 http://www.geographie.uni-bonn.de/deegree/
033
034 e-mail: info@deegree.org
035 ----------------------------------------------------------------------------*/
036
037 package org.deegree.framework.util;
038
039 import java.util.Collection;
040 import java.util.Iterator;
041 import java.util.LinkedHashMap;
042 import java.util.LinkedList;
043 import java.util.Map;
044
045 /**
046 * <code>CollectionUtils</code> contains some functionality missing in <code>Arrays</code> and <code>Collections</code>.
047 *
048 * @author <a href="mailto:schmitz@lat-lon.de">Andreas Schmitz</a>
049 * @author last edited by: $Author: aschmitz $
050 *
051 * @version $Revision: 20893 $, $Date: 2009-11-19 14:31:51 +0100 (Do, 19 Nov 2009) $
052 */
053 public class CollectionUtils {
054
055 /**
056 * @param <T>
057 * @param col
058 * may not contain null values
059 * @param sep
060 * the separating string
061 * @return a comma separated list of #toString values
062 */
063 public static <T> String collectionToString( Collection<T> col, String sep ) {
064 StringBuilder sb = new StringBuilder( 512 );
065
066 Iterator<T> iter = col.iterator();
067
068 while ( iter.hasNext() ) {
069 sb.append( iter.next() );
070 if ( iter.hasNext() ) {
071 sb.append( sep );
072 }
073 }
074
075 return sb.toString();
076 }
077
078 /**
079 * Wraps a for loop and the creation of a new list.
080 *
081 * @param <T>
082 * @param <U>
083 * @param col
084 * @param mapper
085 * @return a list where the mapper has been applied to each element in the map
086 */
087 public static <T, U> LinkedList<T> map( U[] col, Mapper<T, U> mapper ) {
088 LinkedList<T> list = new LinkedList<T>();
089
090 for ( U u : col ) {
091 list.add( mapper.apply( u ) );
092 }
093
094 return list;
095 }
096
097 /**
098 * Wraps a for loop and the creation of a new list.
099 *
100 * @param <T>
101 * @param <U>
102 * @param col
103 * @param mapper
104 * @return a list where the mapper has been applied to each element in the map
105 */
106 public static <T, U> LinkedList<T> map( Collection<U> col, Mapper<T, U> mapper ) {
107 LinkedList<T> list = new LinkedList<T>();
108
109 for ( U u : col ) {
110 list.add( mapper.apply( u ) );
111 }
112
113 return list;
114 }
115
116 /**
117 * @param <T>
118 * @param array
119 * @param obj
120 * @return true, if the object is contained within the array
121 */
122 public static <T> boolean contains( T[] array, T obj ) {
123 for ( T t : array ) {
124 if ( obj == t ) {
125 return true;
126 }
127 }
128
129 return false;
130 }
131
132 /**
133 * @param <T>
134 * @param col
135 * @param obj
136 * @return true, if the object is contained within the collection
137 */
138 public static <T> boolean contains( Collection<T> col, T obj ) {
139 for ( T t : col ) {
140 if ( obj == t ) {
141 return true;
142 }
143 }
144
145 return false;
146 }
147
148 /**
149 * @param <T>
150 * @param col
151 * @param obj
152 * @return true, if an equal object is contained
153 */
154 public static <T> boolean containsEqual( Collection<T> col, T obj ) {
155 for ( T t : col ) {
156 if ( obj.equals( t ) ) {
157 return true;
158 }
159 }
160
161 return false;
162 }
163
164 /**
165 * Attention: runs in n*n
166 *
167 * @param <T>
168 * @param col
169 * @param other
170 * @return true, if all elements in col have an equal in other
171 */
172 public static <T> boolean containsAllEqual( Collection<T> col, Collection<T> other ) {
173 for ( T t : col ) {
174 boolean contains = false;
175 inner: for ( T u : other ) {
176 if ( t.equals( u ) ) {
177 contains = true;
178 break inner;
179 }
180 }
181 if ( !contains ) {
182 return false;
183 }
184 }
185 return true;
186 }
187
188 /**
189 * @param <T>
190 * @param array
191 * @param pred
192 * @return the first object for which the predicate is true, or null
193 */
194 public static <T> T find( T[] array, Predicate<T> pred ) {
195 for ( T t : array ) {
196 if ( pred.eval( t ) ) {
197 return t;
198 }
199 }
200
201 return null;
202 }
203
204 /**
205 * @param <T>
206 * @param col
207 * @param pred
208 * @return the first object for which the predicate is true, or null
209 */
210 public static <T> T find( Collection<T> col, Predicate<T> pred ) {
211 for ( T t : col ) {
212 if ( pred.eval( t ) ) {
213 return t;
214 }
215 }
216
217 return null;
218 }
219
220 /**
221 * @param <T>
222 * @param col
223 * @param pred
224 * @return only those T, for which the pred is true
225 */
226 public static <T> LinkedList<T> filter( Collection<T> col, Predicate<T> pred ) {
227
228 LinkedList<T> list = new LinkedList<T>();
229 for ( T t : col ) {
230 if ( pred.eval( t ) ) {
231 list.add( t );
232 }
233 }
234
235 return list;
236 }
237
238 /**
239 * @param <T>
240 * @param identity
241 * @param col
242 * @param folder
243 * @return the folded value
244 */
245 public static <T> T fold( T identity, Collection<T> col, Folder<T> folder ) {
246 if ( col.isEmpty() ) {
247 return identity;
248 }
249
250 Iterator<T> i = col.iterator();
251
252 T acc = i.next();
253
254 while ( i.hasNext() ) {
255 acc = folder.fold( acc, i.next() );
256 }
257
258 return acc;
259 }
260
261 /**
262 * <code>Predicate</code> defines a boolean predicate function interface.
263 *
264 * @author <a href="mailto:schmitz@lat-lon.de">Andreas Schmitz</a>
265 * @author last edited by: $Author: aschmitz $
266 *
267 * @version $Revision: 20893 $, $Date: 2009-11-19 14:31:51 +0100 (Do, 19 Nov 2009) $
268 * @param <T>
269 * the type of the predicate function's argument
270 */
271 public static interface Predicate<T> {
272 /**
273 * @param t
274 * @return true, if the predicate is satisfied
275 */
276 public boolean eval( T t );
277 }
278
279 /**
280 * <code>Mapper</code> gives a name to a simple function.
281 *
282 * @author <a href="mailto:schmitz@lat-lon.de">Andreas Schmitz</a>
283 * @author last edited by: $Author: aschmitz $
284 *
285 * @version $Revision: 20893 $, $Date: 2009-11-19 14:31:51 +0100 (Do, 19 Nov 2009) $
286 * @param <T>
287 * the return type of the function
288 * @param <U>
289 * the argument type of the function
290 */
291 public static interface Mapper<T, U> {
292 /**
293 * @param u
294 * @return an implementation defined value
295 */
296 public T apply( U u );
297 }
298
299 /**
300 * <code>Folder</code>
301 *
302 * @author <a href="mailto:schmitz@lat-lon.de">Andreas Schmitz</a>
303 * @author last edited by: $Author: aschmitz $
304 *
305 * @version $Revision: 20893 $, $Date: 2009-11-19 14:31:51 +0100 (Do, 19 Nov 2009) $
306 * @param <T>
307 */
308 public static interface Folder<T> {
309 /**
310 * @param t1
311 * @param t2
312 * @return the folded value
313 */
314 public T fold( T t1, T t2 );
315 }
316
317 /**
318 *
319 */
320 public static final Mapper<String, Object> TOSTRINGS = new Mapper<String, Object>() {
321 public String apply( Object u ) {
322 return u.toString();
323 }
324 };
325
326 /**
327 * @param vals
328 * @return the array as list
329 */
330 public static LinkedList<Integer> asList( int[] vals ) {
331 LinkedList<Integer> list = new LinkedList<Integer>();
332 for ( int i : vals ) {
333 list.add( i );
334 }
335 return list;
336 }
337
338 /**
339 * Not quite zip...
340 *
341 * @param <T>
342 * @param <U>
343 * @param col
344 * @return a map with the first pair components mapping to the second
345 */
346 public static <T, U> LinkedHashMap<T, U> unzip( Collection<Pair<T, U>> col ) {
347 LinkedHashMap<T, U> map = new LinkedHashMap<T, U>( col.size() );
348 for ( Pair<T, U> pair : col ) {
349 map.put( pair.first, pair.second );
350 }
351 return map;
352 }
353
354 /**
355 * Not quite unzip...
356 *
357 * @param <T>
358 * @param <U>
359 * @param map
360 * @return a list with the keys paired with their values
361 */
362 public static <T, U> LinkedList<Pair<T, U>> zip( Map<T, U> map ) {
363 LinkedList<Pair<T, U>> list = new LinkedList<Pair<T, U>>();
364 for ( T key : map.keySet() ) {
365 list.add( new Pair<T, U>( key, map.get( key ) ) );
366 }
367 return list;
368 }
369
370 /**
371 * @param <T>
372 * @param ts
373 * @return the last element or null
374 */
375 public static <T> T last( T[] ts ) {
376 return ts == null || ts.length == 0 ? null : ts[ts.length - 1];
377 }
378
379 }