    001    //$HeadURL: https://svn.wald.intevation.org/svn/deegree/base/branches/2.4_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    }