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/*
 *  Copyright 2001-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.collection.PredicatedCollection;
import org.apache.commons.collections.collection.SynchronizedCollection;
import org.apache.commons.collections.collection.TransformedCollection;
import org.apache.commons.collections.collection.TypedCollection;
import org.apache.commons.collections.collection.UnmodifiableBoundedCollection;
import org.apache.commons.collections.collection.UnmodifiableCollection;

/**
 * Provides utility methods and decorators for {@link Collection} instances.
 *
 * @since Commons Collections 1.0
 * @version $Revision: 1.61 $ $Date: 2004/04/27 20:00:18 $
 * 
 * @author Rodney Waldhoff
 * @author Paul Jack
 * @author Stephen Colebourne
 * @author Steve Downey
 * @author Herve Quiroz
 * @author Peter KoBek
 * @author Matthew Hawthorne
 * @author Janek Bogucki
 * @author Phil Steitz
 * @author Steven Melzer
 * @author Jon Schewe
 */
public class CollectionUtils {

	/** Constant to avoid repeated object creation */
    private static Integer INTEGER_ONE = new Integer(1);

    /**
     * An empty unmodifiable collection.
     * The JDK provides empty Set and List implementations which could be used for
     * this purpose. However they could be cast to Set or List which might be
     * undesirable. This implementation only implements Collection.
     */
    public static final Collection EMPTY_COLLECTION = UnmodifiableCollection.decorate(new ArrayList());

    /**
     * CollectionUtils should not normally be instantiated.
     */
    public CollectionUtils() {
    }

    /**
     * Returns a {@link Collection} containing the union
     * of the given {@link Collection}s.
     * 

* The cardinality of each element in the returned {@link Collection} * will be equal to the maximum of the cardinality of that element * in the two given {@link Collection}s. * * @param a the first collection, must not be null * @param b the second collection, must not be null * @return the union of the two collections * @see Collection#addAll */ public static Collection union(final Collection a, final Collection b) { ArrayList list = new ArrayList(); Map mapa = getCardinalityMap(a); Map mapb = getCardinalityMap(b); Set elts = new HashSet(a); elts.addAll(b); Iterator it = elts.iterator(); while(it.hasNext()) { Object obj = it.next(); for(int i=0,m=Math.max(getFreq(obj,mapa),getFreq(obj,mapb));i * The cardinality of each element in the returned {@link Collection} * will be equal to the minimum of the cardinality of that element * in the two given {@link Collection}s. * * @param a the first collection, must not be null * @param b the second collection, must not be null * @return the intersection of the two collections * @see Collection#retainAll * @see #containsAny */ public static Collection intersection(final Collection a, final Collection b) { ArrayList list = new ArrayList(); Map mapa = getCardinalityMap(a); Map mapb = getCardinalityMap(b); Set elts = new HashSet(a); elts.addAll(b); Iterator it = elts.iterator(); while(it.hasNext()) { Object obj = it.next(); for(int i=0,m=Math.min(getFreq(obj,mapa),getFreq(obj,mapb));i * The cardinality of each element e in the returned {@link Collection} * will be equal to * max(cardinality(e,a),cardinality(e,b)) - min(cardinality(e,a),cardinality(e,b)). *

* This is equivalent to * {@link #subtract subtract}({@link #union union(a,b)},{@link #intersection intersection(a,b)}) * or * {@link #union union}({@link #subtract subtract(a,b)},{@link #subtract subtract(b,a)}). * * @param a the first collection, must not be null * @param b the second collection, must not be null * @return the symmetric difference of the two collections */ public static Collection disjunction(final Collection a, final Collection b) { ArrayList list = new ArrayList(); Map mapa = getCardinalityMap(a); Map mapb = getCardinalityMap(b); Set elts = new HashSet(a); elts.addAll(b); Iterator it = elts.iterator(); while(it.hasNext()) { Object obj = it.next(); for(int i=0,m=((Math.max(getFreq(obj,mapa),getFreq(obj,mapb)))-(Math.min(getFreq(obj,mapa),getFreq(obj,mapb))));ia - b. * The cardinality of each element e in the returned {@link Collection} * will be the cardinality of e in a minus the cardinality * of e in b, or zero, whichever is greater. * * @param a the collection to subtract from, must not be null * @param b the collection to subtract, must not be null * @return a new collection with the results * @see Collection#removeAll */ public static Collection subtract(final Collection a, final Collection b) { ArrayList list = new ArrayList( a ); for (Iterator it = b.iterator(); it.hasNext();) { list.remove(it.next()); } return list; } /** * Returns true iff at least one element is in both collections. *

* In other words, this method returns true iff the * {@link #intersection} of coll1 and coll2 is not empty. * * @param coll1 the first collection, must not be null * @param coll2 the first collection, must not be null * @return true iff the intersection of the collections is non-empty * @since 2.1 * @see #intersection */ public static boolean containsAny(final Collection coll1, final Collection coll2) { if (coll1.size() < coll2.size()) { for (Iterator it = coll1.iterator(); it.hasNext();) { if (coll2.contains(it.next())) { return true; } } } else { for (Iterator it = coll2.iterator(); it.hasNext();) { if (coll1.contains(it.next())) { return true; } } } return false; } /** * Returns a {@link Map} mapping each unique element in the given * {@link Collection} to an {@link Integer} representing the number * of occurrences of that element in the {@link Collection}. *

* Only those elements present in the collection will appear as * keys in the map. * * @param coll the collection to get the cardinality map for, must not be null * @return the populated cardinality map */ public static Map getCardinalityMap(final Collection coll) { Map count = new HashMap(); for (Iterator it = coll.iterator(); it.hasNext();) { Object obj = it.next(); Integer c = (Integer) (count.get(obj)); if (c == null) { count.put(obj,INTEGER_ONE); } else { count.put(obj,new Integer(c.intValue() + 1)); } } return count; } /** * Returns true iff a is a sub-collection of b, * that is, iff the cardinality of e in a is less * than or equal to the cardinality of e in b, * for each element e in a. * * @param a the first (sub?) collection, must not be null * @param b the second (super?) collection, must not be null * @return true iff a is a sub-collection of b * @see #isProperSubCollection * @see Collection#containsAll */ public static boolean isSubCollection(final Collection a, final Collection b) { Map mapa = getCardinalityMap(a); Map mapb = getCardinalityMap(b); Iterator it = a.iterator(); while (it.hasNext()) { Object obj = it.next(); if (getFreq(obj, mapa) > getFreq(obj, mapb)) { return false; } } return true; } /** * Returns true iff a is a proper sub-collection of b, * that is, iff the cardinality of e in a is less * than or equal to the cardinality of e in b, * for each element e in a, and there is at least one * element f such that the cardinality of f in b * is strictly greater than the cardinality of f in a. *

* The implementation assumes *

    *
  • a.size() and b.size() represent the * total cardinality of a and b, resp.
  • *
  • a.size() < Integer.MAXVALUE
  • *
* * @param a the first (sub?) collection, must not be null * @param b the second (super?) collection, must not be null * @return true iff a is a proper sub-collection of b * @see #isSubCollection * @see Collection#containsAll */ public static boolean isProperSubCollection(final Collection a, final Collection b) { return (a.size() < b.size()) && CollectionUtils.isSubCollection(a,b); } /** * Returns true iff the given {@link Collection}s contain * exactly the same elements with exactly the same cardinalities. *

* That is, iff the cardinality of e in a is * equal to the cardinality of e in b, * for each element e in a or b. * * @param a the first collection, must not be null * @param b the second collection, must not be null * @return true iff the collections contain the same elements with the same cardinalities. */ public static boolean isEqualCollection(final Collection a, final Collection b) { if(a.size() != b.size()) { return false; } else { Map mapa = getCardinalityMap(a); Map mapb = getCardinalityMap(b); if(mapa.size() != mapb.size()) { return false; } else { Iterator it = mapa.keySet().iterator(); while(it.hasNext()) { Object obj = it.next(); if(getFreq(obj,mapa) != getFreq(obj,mapb)) { return false; } } return true; } } } /** * Returns the number of occurrences of obj in coll. * * @param obj the object to find the cardinality of * @param coll the collection to search * @return the the number of occurrences of obj in coll */ public static int cardinality(Object obj, final Collection coll) { if (coll instanceof Set) { return (coll.contains(obj) ? 1 : 0); } if (coll instanceof Bag) { return ((Bag) coll).getCount(obj); } int count = 0; if (obj == null) { for (Iterator it = coll.iterator();it.hasNext();) { if (it.next() == null) { count++; } } } else { for (Iterator it = coll.iterator();it.hasNext();) { if (obj.equals(it.next())) { count++; } } } return count; } /** * Finds the first element in the given collection which matches the given predicate. *

* If the input collection or predicate is null, or no element of the collection * matches the predicate, null is returned. * * @param collection the collection to search, may be null * @param predicate the predicate to use, may be null * @return the first element of the collection which matches the predicate or null if none could be found */ public static Object find(Collection collection, Predicate predicate) { if (collection != null && predicate != null) { for (Iterator iter = collection.iterator(); iter.hasNext();) { Object item = iter.next(); if (predicate.evaluate(item)) { return item; } } } return null; } /** * Executes the given closure on each element in the collection. *

* If the input collection or closure is null, there is no change made. * * @param collection the collection to get the input from, may be null * @param closure the closure to perform, may be null */ public static void forAllDo(Collection collection, Closure closure) { if (collection != null && closure != null) { for (Iterator it = collection.iterator(); it.hasNext();) { closure.execute(it.next()); } } } /** * Filter the collection by applying a Predicate to each element. If the * predicate returns false, remove the element. *

* If the input collection or predicate is null, there is no change made. * * @param collection the collection to get the input from, may be null * @param predicate the predicate to use as a filter, may be null */ public static void filter(Collection collection, Predicate predicate) { if (collection != null && predicate != null) { for (Iterator it = collection.iterator(); it.hasNext();) { if (predicate.evaluate(it.next()) == false) { it.remove(); } } } } /** * Transform the collection by applying a Transformer to each element. *

* If the input collection or transformer is null, there is no change made. *

* This routine is best for Lists, for which set() is used to do the * transformations "in place." For other Collections, clear() and addAll() * are used to replace elements. *

* If the input collection controls its input, such as a Set, and the * Transformer creates duplicates (or are otherwise invalid), the * collection may reduce in size due to calling this method. * * @param collection the collection to get the input from, may be null * @param transformer the transformer to perform, may be null */ public static void transform(Collection collection, Transformer transformer) { if (collection != null && transformer != null) { if (collection instanceof List) { List list = (List) collection; for (ListIterator it = list.listIterator(); it.hasNext();) { it.set(transformer.transform(it.next())); } } else { Collection resultCollection = collect(collection, transformer); collection.clear(); collection.addAll(resultCollection); } } } /** * Counts the number of elements in the input collection that match the predicate. *

* A null collection or predicate matches no elements. * * @param inputCollection the collection to get the input from, may be null * @param predicate the predicate to use, may be null * @return the number of matches for the predicate in the collection */ public static int countMatches(Collection inputCollection, Predicate predicate) { int count = 0; if (inputCollection != null && predicate != null) { for (Iterator it = inputCollection.iterator(); it.hasNext();) { if (predicate.evaluate(it.next())) { count++; } } } return count; } /** * Answers true if a predicate is true for at least one element of a collection. *

* A null collection or predicate returns false. * * @param collection the collection to get the input from, may be null * @param predicate the predicate to use, may be null * @return true if at least one element of the collection matches the predicate */ public static boolean exists(Collection collection, Predicate predicate) { if (collection != null && predicate != null) { for (Iterator it = collection.iterator(); it.hasNext();) { if (predicate.evaluate(it.next())) { return true; } } } return false; } /** * Selects all elements from input collection which match the given predicate * into an output collection. *

* A null predicate matches no elements. * * @param inputCollection the collection to get the input from, may not be null * @param predicate the predicate to use, may be null * @return the elements matching the predicate (new list) * @throws NullPointerException if the input collection is null */ public static Collection select(Collection inputCollection, Predicate predicate) { ArrayList answer = new ArrayList(inputCollection.size()); select(inputCollection, predicate, answer); return answer; } /** * Selects all elements from input collection which match the given predicate * and adds them to outputCollection. *

* If the input collection or predicate is null, there is no change to the * output collection. * * @param inputCollection the collection to get the input from, may be null * @param predicate the predicate to use, may be null * @param outputCollection the collection to output into, may not be null */ public static void select(Collection inputCollection, Predicate predicate, Collection outputCollection) { if (inputCollection != null && predicate != null) { for (Iterator iter = inputCollection.iterator(); iter.hasNext();) { Object item = iter.next(); if (predicate.evaluate(item)) { outputCollection.add(item); } } } } /** * Selects all elements from inputCollection which don't match the given predicate * into an output collection. *

* If the input predicate is null, the result is an empty list. * * @param inputCollection the collection to get the input from, may not be null * @param predicate the predicate to use, may be null * @return the elements not matching the predicate (new list) * @throws NullPointerException if the input collection is null */ public static Collection selectRejected(Collection inputCollection, Predicate predicate) { ArrayList answer = new ArrayList(inputCollection.size()); selectRejected(inputCollection, predicate, answer); return answer; } /** * Selects all elements from inputCollection which don't match the given predicate * and adds them to outputCollection. *

* If the input predicate is null, no elements are added to outputCollection. * * @param inputCollection the collection to get the input from, may be null * @param predicate the predicate to use, may be null * @param outputCollection the collection to output into, may not be null */ public static void selectRejected(Collection inputCollection, Predicate predicate, Collection outputCollection) { if (inputCollection != null && predicate != null) { for (Iterator iter = inputCollection.iterator(); iter.hasNext();) { Object item = iter.next(); if (predicate.evaluate(item) == false) { outputCollection.add(item); } } } } /** * Returns a new Collection consisting of the elements of inputCollection transformed * by the given transformer. *

* If the input transformer is null, the result is an empty list. * * @param inputCollection the collection to get the input from, may not be null * @param transformer the transformer to use, may be null * @return the transformed result (new list) * @throws NullPointerException if the input collection is null */ public static Collection collect(Collection inputCollection, Transformer transformer) { ArrayList answer = new ArrayList(inputCollection.size()); collect(inputCollection, transformer, answer); return answer; } /** * Transforms all elements from the inputIterator with the given transformer * and adds them to the outputCollection. *

* If the input iterator or transformer is null, the result is an empty list. * * @param inputIterator the iterator to get the input from, may be null * @param transformer the transformer to use, may be null * @return the transformed result (new list) */ public static Collection collect(Iterator inputIterator, Transformer transformer) { ArrayList answer = new ArrayList(); collect(inputIterator, transformer, answer); return answer; } /** * Transforms all elements from inputCollection with the given transformer * and adds them to the outputCollection. *

* If the input collection or transformer is null, there is no change to the * output collection. * * @param inputCollection the collection to get the input from, may be null * @param transformer the transformer to use, may be null * @param outputCollection the collection to output into, may not be null * @return the outputCollection with the transformed input added * @throws NullPointerException if the output collection is null */ public static Collection collect(Collection inputCollection, final Transformer transformer, final Collection outputCollection) { if (inputCollection != null) { return collect(inputCollection.iterator(), transformer, outputCollection); } return outputCollection; } /** * Transforms all elements from the inputIterator with the given transformer * and adds them to the outputCollection. *

* If the input iterator or transformer is null, there is no change to the * output collection. * * @param inputIterator the iterator to get the input from, may be null * @param transformer the transformer to use, may be null * @param outputCollection the collection to output into, may not be null * @return the outputCollection with the transformed input added * @throws NullPointerException if the output collection is null */ public static Collection collect(Iterator inputIterator, final Transformer transformer, final Collection outputCollection) { if (inputIterator != null && transformer != null) { while (inputIterator.hasNext()) { Object item = inputIterator.next(); Object value = transformer.transform(item); outputCollection.add(value); } } return outputCollection; } /** * Adds all elements in the iteration to the given collection. * * @param collection the collection to add to * @param iterator the iterator of elements to add, may not be null * @throws NullPointerException if the collection or iterator is null */ public static void addAll(Collection collection, Iterator iterator) { while (iterator.hasNext()) { collection.add(iterator.next()); } } /** * Adds all elements in the enumeration to the given collection. * * @param collection the collection to add to * @param enumeration the enumeration of elements to add, may not be null * @throws NullPointerException if the collection or enumeration is null */ public static void addAll(Collection collection, Enumeration enumeration) { while (enumeration.hasMoreElements()) { collection.add(enumeration.nextElement()); } } /** * Adds all elements in the array to the given collection. * * @param collection the collection to add to, may not be null * @param elements the array of elements to add, may not be null * @throws NullPointerException if the collection or array is null */ public static void addAll(Collection collection, Object[] elements) { for (int i = 0, size = elements.length; i < size; i++) { collection.add(elements[i]); } } /** * Given an Object, and an index, returns the nth value in the * object. *

    *
  • If obj is a Map, returns the nth value from the keySet iterator, unless * the Map contains an Integer key with integer value = idx, in which case the * corresponding map entry value is returned. If idx exceeds the number of entries in * the map, an empty Iterator is returned. *
  • If obj is a List or an array, returns the nth value, throwing IndexOutOfBoundsException, * ArrayIndexOutOfBoundsException, resp. if the nth value does not exist. *
  • If obj is an iterator, enumeration or Collection, returns the nth value from the iterator, * returning an empty Iterator (resp. Enumeration) if the nth value does not exist. *
  • Returns the original obj if it is null or not a Collection or Iterator. *
* * @param obj the object to get an index of, may be null * @param idx the index to get * @throws IndexOutOfBoundsException * @throws ArrayIndexOutOfBoundsException * * @deprecated use {@link #get(Object, int)} instead. Will be removed in v4.0 */ public static Object index(Object obj, int idx) { return index(obj, new Integer(idx)); } /** * Given an Object, and a key (index), returns the value associated with * that key in the Object. The following checks are made: *
    *
  • If obj is a Map, use the index as a key to get a value. If no match continue. *
  • Check key is an Integer. If not, return the object passed in. *
  • If obj is a Map, get the nth value from the keySet iterator. * If the Map has fewer than n entries, return an empty Iterator. *
  • If obj is a List or an array, get the nth value, throwing IndexOutOfBoundsException, * ArrayIndexOutOfBoundsException, resp. if the nth value does not exist. *
  • If obj is an iterator, enumeration or Collection, get the nth value from the iterator, * returning an empty Iterator (resp. Enumeration) if the nth value does not exist. *
  • Return the original obj. *
* * @param obj the object to get an index of * @param index the index to get * @return the object at the specified index * @throws IndexOutOfBoundsException * @throws ArrayIndexOutOfBoundsException * * @deprecated use {@link #get(Object, int)} instead. Will be removed in v4.0 */ public static Object index(Object obj, Object index) { if(obj instanceof Map) { Map map = (Map)obj; if(map.containsKey(index)) { return map.get(index); } } int idx = -1; if(index instanceof Integer) { idx = ((Integer)index).intValue(); } if(idx < 0) { return obj; } else if(obj instanceof Map) { Map map = (Map)obj; Iterator iterator = map.keySet().iterator(); return index(iterator, idx); } else if(obj instanceof List) { return ((List)obj).get(idx); } else if(obj instanceof Object[]) { return ((Object[])obj)[idx]; } else if(obj instanceof Enumeration) { Enumeration it = (Enumeration)obj; while(it.hasMoreElements()) { idx--; if(idx == -1) { return it.nextElement(); } else { it.nextElement(); } } } else if(obj instanceof Iterator) { return index((Iterator)obj, idx); } else if(obj instanceof Collection) { Iterator iterator = ((Collection)obj).iterator(); return index(iterator, idx); } return obj; } private static Object index(Iterator iterator, int idx) { while(iterator.hasNext()) { idx--; if(idx == -1) { return iterator.next(); } else { iterator.next(); } } return iterator; } /** * Returns the index-th value in object, throwing * IndexOutOfBoundsException if there is no such element or * IllegalArgumentException if object is not an * instance of one of the supported types. *

* The supported types, and associated semantics are: *

    *
  • Map -- the value returned is the Map.Entry in position * index in the map's entrySet iterator, * if there is such an entry.
  • *
  • List -- this method is equivalent to the list's get method.
  • *
  • Array -- the index-th array entry is returned, * if there is such an entry; otherwise an IndexOutOfBoundsException * is thrown.
  • *
  • Collection -- the value returned is the index-th object * returned by the collection's default iterator, if there is such an element.
  • *
  • Iterator or Enumeration -- the value returned is the * index-th object in the Iterator/Enumeration, if there * is such an element. The Iterator/Enumeration is advanced to * index (or to the end, if index exceeds the * number of entries) as a side effect of this method.
  • *
* * @param object the object to get a value from * @param index the index to get * @return the object at the specified index * @throws IndexOutOfBoundsException if the index is invalid * @throws IllegalArgumentException if the object type is invalid */ public static Object get(Object object, int index) { if (index < 0) { throw new IndexOutOfBoundsException("Index cannot be negative: " + index); } if (object instanceof Map) { Map map = (Map) object; Iterator iterator = map.entrySet().iterator(); return get(iterator, index); } else if (object instanceof List) { return ((List) object).get(index); } else if (object instanceof Object[]) { return ((Object[]) object)[index]; } else if (object instanceof Iterator) { Iterator it = (Iterator) object; while (it.hasNext()) { index--; if (index == -1) { return it.next(); } else { it.next(); } } throw new IndexOutOfBoundsException("Entry does not exist: " + index); } else if (object instanceof Collection) { Iterator iterator = ((Collection) object).iterator(); return get(iterator, index); } else if (object instanceof Enumeration) { Enumeration it = (Enumeration) object; while (it.hasMoreElements()) { index--; if (index == -1) { return it.nextElement(); } else { it.nextElement(); } } throw new IndexOutOfBoundsException("Entry does not exist: " + index); } else if (object == null) { throw new IllegalArgumentException("Unsupported object type: null"); } else { try { return Array.get(object, index); } catch (IllegalArgumentException ex) { throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName()); } } } /** * Gets the size of the collection/iterator specified. *

* This method can handles objects as follows *

    *
  • Collection - the collection size *
  • Map - the map size *
  • Array - the array size *
  • Iterator - the number of elements remaining in the iterator *
  • Enumeration - the number of elements remaining in the enumeration *
* * @param object the object to get the size of * @return the size of the specified collection * @throws IllegalArgumentException thrown if object is not recognised or null * @since Commons Collections 3.1 */ public static int size(Object object) { int total = 0; if (object instanceof Map) { total = ((Map) object).size(); } else if (object instanceof Collection) { total = ((Collection) object).size(); } else if (object instanceof Object[]) { total = ((Object[]) object).length; } else if (object instanceof Iterator) { Iterator it = (Iterator) object; while (it.hasNext()) { total++; it.next(); } } else if (object instanceof Enumeration) { Enumeration it = (Enumeration) object; while (it.hasMoreElements()) { total++; it.nextElement(); } } else if (object == null) { throw new IllegalArgumentException("Unsupported object type: null"); } else { try { total = Array.getLength(object); } catch (IllegalArgumentException ex) { throw new IllegalArgumentException("Unsupported object type: " + object.getClass().getName()); } } return total; } /** * Reverses the order of the given array. * * @param array the array to reverse */ public static void reverseArray(Object[] array) { int i = 0; int j = array.length - 1; Object tmp; while (j > i) { tmp = array[j]; array[j] = array[i]; array[i] = tmp; j--; i++; } } private static final int getFreq(final Object obj, final Map freqMap) { Integer count = (Integer) freqMap.get(obj); if (count != null) { return count.intValue(); } return 0; } /** * Returns true if no more elements can be added to the Collection. *

* This method uses the {@link BoundedCollection} interface to determine the * full status. If the collection does not implement this interface then * false is returned. *

* The collection does not have to implement this interface directly. * If the collection has been decorated using the decorators subpackage * then these will be removed to access the BoundedCollection. * * @param coll the collection to check * @return true if the BoundedCollection is full * @throws NullPointerException if the collection is null */ public static boolean isFull(Collection coll) { if (coll == null) { throw new NullPointerException("The collection must not be null"); } if (coll instanceof BoundedCollection) { return ((BoundedCollection) coll).isFull(); } try { BoundedCollection bcoll = UnmodifiableBoundedCollection.decorateUsing(coll); return bcoll.isFull(); } catch (IllegalArgumentException ex) { return false; } } /** * Get the maximum number of elements that the Collection can contain. *

* This method uses the {@link BoundedCollection} interface to determine the * maximum size. If the collection does not implement this interface then * -1 is returned. *

* The collection does not have to implement this interface directly. * If the collection has been decorated using the decorators subpackage * then these will be removed to access the BoundedCollection. * * @param coll the collection to check * @return the maximum size of the BoundedCollection, -1 if no maximum size * @throws NullPointerException if the collection is null */ public static int maxSize(Collection coll) { if (coll == null) { throw new NullPointerException("The collection must not be null"); } if (coll instanceof BoundedCollection) { return ((BoundedCollection) coll).maxSize(); } try { BoundedCollection bcoll = UnmodifiableBoundedCollection.decorateUsing(coll); return bcoll.maxSize(); } catch (IllegalArgumentException ex) { return -1; } } //----------------------------------------------------------------------- /** * Returns a synchronized collection backed by the given collection. *

* You must manually synchronize on the returned buffer's iterator to * avoid non-deterministic behavior: * *

     * Collection c = CollectionUtils.synchronizedCollection(myCollection);
     * synchronized (c) {
     *     Iterator i = c.iterator();
     *     while (i.hasNext()) {
     *         process (i.next());
     *     }
     * }
     * 
* * This method uses the implementation in the decorators subpackage. * * @param collection the collection to synchronize, must not be null * @return a synchronized collection backed by the given collection * @throws IllegalArgumentException if the collection is null */ public static Collection synchronizedCollection(Collection collection) { return SynchronizedCollection.decorate(collection); } /** * Returns an unmodifiable collection backed by the given collection. *

* This method uses the implementation in the decorators subpackage. * * @param collection the collection to make unmodifiable, must not be null * @return an unmodifiable collection backed by the given collection * @throws IllegalArgumentException if the collection is null */ public static Collection unmodifiableCollection(Collection collection) { return UnmodifiableCollection.decorate(collection); } /** * Returns a predicated (validating) collection backed by the given collection. *

* Only objects that pass the test in the given predicate can be added to the collection. * Trying to add an invalid object results in an IllegalArgumentException. * It is important not to use the original collection after invoking this method, * as it is a backdoor for adding invalid objects. * * @param collection the collection to predicate, must not be null * @param predicate the predicate for the collection, must not be null * @return a predicated collection backed by the given collection * @throws IllegalArgumentException if the Collection is null */ public static Collection predicatedCollection(Collection collection, Predicate predicate) { return PredicatedCollection.decorate(collection, predicate); } /** * Returns a typed collection backed by the given collection. *

* Only objects of the specified type can be added to the collection. * * @param collection the collection to limit to a specific type, must not be null * @param type the type of objects which may be added to the collection * @return a typed collection backed by the specified collection */ public static Collection typedCollection(Collection collection, Class type) { return TypedCollection.decorate(collection, type); } /** * Returns a transformed bag backed by the given collection. *

* Each object is passed through the transformer as it is added to the * Collection. It is important not to use the original collection after invoking this * method, as it is a backdoor for adding untransformed objects. * * @param collection the collection to predicate, must not be null * @param transformer the transformer for the collection, must not be null * @return a transformed collection backed by the given collection * @throws IllegalArgumentException if the Collection or Transformer is null */ public static Collection transformedCollection(Collection collection, Transformer transformer) { return TransformedCollection.decorate(collection, transformer); } }

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