java.lang.Object
- org.apache.commons.collections.CollectionUtils

```
@Deprecated(since="2021-04-30")
public class CollectionUtils
extends java.lang.Object
```
Deprecated.
Commons Collections 3 is in maintenance mode. Commons Collections 4 should be used instead.

Provides utility methods and decorators for Collection instances.

Since:

Commons Collections 1.0

Field Summary

Fields
Modifier and Type Field Description

static java.util.Collection EMPTY_COLLECTION
Deprecated.

An empty unmodifiable collection.

Constructor Summary

Constructors
Constructor Description

CollectionUtils()
Deprecated.

CollectionUtils should not normally be instantiated.

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`static void`	`addAll(java.util.Collection collection, java.lang.Object[] elements)`	Deprecated. Adds all elements in the array to the given collection.
`static void`	`addAll(java.util.Collection collection, java.util.Enumeration enumeration)`	Deprecated. Adds all elements in the enumeration to the given collection.
`static void`	`addAll(java.util.Collection collection, java.util.Iterator iterator)`	Deprecated. Adds all elements in the iteration to the given collection.
`static boolean`	`addIgnoreNull(java.util.Collection collection, java.lang.Object object)`	Deprecated. Adds an element to the collection unless the element is null.
`static int`	`cardinality(java.lang.Object obj, java.util.Collection coll)`	Deprecated. Returns the number of occurrences of obj in coll.
`static java.util.Collection`	`collect(java.util.Collection inputCollection, Transformer transformer)`	Deprecated. Returns a new Collection consisting of the elements of inputCollection transformed by the given transformer.
`static java.util.Collection`	`collect(java.util.Collection inputCollection, Transformer transformer, java.util.Collection outputCollection)`	Deprecated. Transforms all elements from inputCollection with the given transformer and adds them to the outputCollection.
`static java.util.Collection`	`collect(java.util.Iterator inputIterator, Transformer transformer)`	Deprecated. Transforms all elements from the inputIterator with the given transformer and adds them to the outputCollection.
`static java.util.Collection`	`collect(java.util.Iterator inputIterator, Transformer transformer, java.util.Collection outputCollection)`	Deprecated. Transforms all elements from the inputIterator with the given transformer and adds them to the outputCollection.
`static boolean`	`containsAny(java.util.Collection coll1, java.util.Collection coll2)`	Deprecated. Returns `true` iff at least one element is in both collections.
`static int`	`countMatches(java.util.Collection inputCollection, Predicate predicate)`	Deprecated. Counts the number of elements in the input collection that match the predicate.
`static java.util.Collection`	`disjunction(java.util.Collection a, java.util.Collection b)`	Deprecated. Returns a `Collection` containing the exclusive disjunction (symmetric difference) of the given `Collection`s.
`static boolean`	`exists(java.util.Collection collection, Predicate predicate)`	Deprecated. Answers true if a predicate is true for at least one element of a collection.
`static void`	`filter(java.util.Collection collection, Predicate predicate)`	Deprecated. Filter the collection by applying a Predicate to each element.
`static java.lang.Object`	`find(java.util.Collection collection, Predicate predicate)`	Deprecated. Finds the first element in the given collection which matches the given predicate.
`static void`	`forAllDo(java.util.Collection collection, Closure closure)`	Deprecated. Executes the given closure on each element in the collection.
`static java.lang.Object`	`get(java.lang.Object object, int index)`	Deprecated. 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.
`static java.util.Map`	`getCardinalityMap(java.util.Collection coll)`	Deprecated. Returns a `Map` mapping each unique element in the given `Collection` to an `Integer` representing the number of occurrences of that element in the `Collection`.
`static java.lang.Object`	`index(java.lang.Object obj, int idx)`	Deprecated. use `get(Object, int)` instead.
`static java.lang.Object`	`index(java.lang.Object obj, java.lang.Object index)`	Deprecated. use `get(Object, int)` instead.
`static java.util.Collection`	`intersection(java.util.Collection a, java.util.Collection b)`	Deprecated. Returns a `Collection` containing the intersection of the given `Collection`s.
`static boolean`	`isEmpty(java.util.Collection coll)`	Deprecated. Null-safe check if the specified collection is empty.
`static boolean`	`isEqualCollection(java.util.Collection a, java.util.Collection b)`	Deprecated. Returns `true` iff the given `Collection`s contain exactly the same elements with exactly the same cardinalities.
`static boolean`	`isFull(java.util.Collection coll)`	Deprecated. Returns true if no more elements can be added to the Collection.
`static boolean`	`isNotEmpty(java.util.Collection coll)`	Deprecated. Null-safe check if the specified collection is not empty.
`static boolean`	`isProperSubCollection(java.util.Collection a, java.util.Collection b)`	Deprecated. 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.
`static boolean`	`isSubCollection(java.util.Collection a, java.util.Collection b)`	Deprecated. 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.
`static int`	`maxSize(java.util.Collection coll)`	Deprecated. Get the maximum number of elements that the Collection can contain.
`static java.util.Collection`	`predicatedCollection(java.util.Collection collection, Predicate predicate)`	Deprecated. Returns a predicated (validating) collection backed by the given collection.
`static java.util.Collection`	`removeAll(java.util.Collection collection, java.util.Collection remove)`	Deprecated. Removes the elements in `remove` from `collection`.
`static java.util.Collection`	`retainAll(java.util.Collection collection, java.util.Collection retain)`	Deprecated. Returns a collection containing all the elements in `collection` that are also in `retain`.
`static void`	`reverseArray(java.lang.Object[] array)`	Deprecated. Reverses the order of the given array.
`static java.util.Collection`	`select(java.util.Collection inputCollection, Predicate predicate)`	Deprecated. Selects all elements from input collection which match the given predicate into an output collection.
`static void`	`select(java.util.Collection inputCollection, Predicate predicate, java.util.Collection outputCollection)`	Deprecated. Selects all elements from input collection which match the given predicate and adds them to outputCollection.
`static java.util.Collection`	`selectRejected(java.util.Collection inputCollection, Predicate predicate)`	Deprecated. Selects all elements from inputCollection which don't match the given predicate into an output collection.
`static void`	`selectRejected(java.util.Collection inputCollection, Predicate predicate, java.util.Collection outputCollection)`	Deprecated. Selects all elements from inputCollection which don't match the given predicate and adds them to outputCollection.
`static int`	`size(java.lang.Object object)`	Deprecated. Gets the size of the collection/iterator specified.
`static boolean`	`sizeIsEmpty(java.lang.Object object)`	Deprecated. Checks if the specified collection/array/iterator is empty.
`static java.util.Collection`	`subtract(java.util.Collection a, java.util.Collection b)`	Deprecated. Returns a new `Collection` containing `a - b`.
`static java.util.Collection`	`synchronizedCollection(java.util.Collection collection)`	Deprecated. Returns a synchronized collection backed by the given collection.
`static void`	`transform(java.util.Collection collection, Transformer transformer)`	Deprecated. Transform the collection by applying a Transformer to each element.
`static java.util.Collection`	`transformedCollection(java.util.Collection collection, Transformer transformer)`	Deprecated. Returns a transformed bag backed by the given collection.
`static java.util.Collection`	`typedCollection(java.util.Collection collection, java.lang.Class type)`	Deprecated. Returns a typed collection backed by the given collection.
`static java.util.Collection`	`union(java.util.Collection a, java.util.Collection b)`	Deprecated. Returns a `Collection` containing the union of the given `Collection`s.
`static java.util.Collection`	`unmodifiableCollection(java.util.Collection collection)`	Deprecated. Returns an unmodifiable collection backed by the given collection.

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - EMPTY_COLLECTION
```
public static final java.util.Collection EMPTY_COLLECTION
```
    Deprecated.
    
    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.
- Constructor Detail
  - CollectionUtils
```
public CollectionUtils()
```
    Deprecated.
    
    CollectionUtils should not normally be instantiated.
- Method Detail
  - union
```
public static java.util.Collection union(java.util.Collection a,
                                         java.util.Collection b)
```
    Deprecated.
    
    Returns a Collection containing the union of the given Collections.
    The cardinality of each element in the returned Collection will be equal to the maximum of the cardinality of that element in the two given Collections.
    
    Parameters:
    
    a - the first collection, must not be null
    
    b - the second collection, must not be null
    
    Returns:
    
    the union of the two collections
    
    See Also:
    
    Collection.addAll(java.util.Collection<? extends E>)
  - intersection
```
public static java.util.Collection intersection(java.util.Collection a,
                                                java.util.Collection b)
```
    Deprecated.
    
    Returns a Collection containing the intersection of the given Collections.
    The cardinality of each element in the returned Collection will be equal to the minimum of the cardinality of that element in the two given Collections.
    
    Parameters:
    
    a - the first collection, must not be null
    
    b - the second collection, must not be null
    
    Returns:
    
    the intersection of the two collections
    
    See Also:
    
    Collection.retainAll(java.util.Collection<?>), containsAny(java.util.Collection, java.util.Collection)
  - disjunction
```
public static java.util.Collection disjunction(java.util.Collection a,
                                               java.util.Collection b)
```
    Deprecated.
    
    Returns a Collection containing the exclusive disjunction (symmetric difference) of the given Collections.
    The cardinality of each element e in the returned Collection will be equal to max(cardinality(e,a),cardinality(e,b)) - min(cardinality(e,a),cardinality(e,b)).
    This is equivalent to subtract(union(a,b),intersection(a,b)) or union(subtract(a,b),subtract(b,a)).
    
    Parameters:
    
    a - the first collection, must not be null
    
    b - the second collection, must not be null
    
    Returns:
    
    the symmetric difference of the two collections
  - subtract
```
public static java.util.Collection subtract(java.util.Collection a,
                                            java.util.Collection b)
```
    Deprecated.
    
    Returns a new Collection containing a - b. The cardinality of each element e in the returned Collection will be the cardinality of e in a minus the cardinality of e in b, or zero, whichever is greater.
    
    Parameters:
    
    a - the collection to subtract from, must not be null
    
    b - the collection to subtract, must not be null
    
    Returns:
    
    a new collection with the results
    
    See Also:
    
    Collection.removeAll(java.util.Collection<?>)
  - containsAny
```
public static boolean containsAny(java.util.Collection coll1,
                                  java.util.Collection coll2)
```
    Deprecated.
    
    Returns true iff at least one element is in both collections.
    In other words, this method returns true iff the intersection(java.util.Collection, java.util.Collection) of coll1 and coll2 is not empty.
    
    Parameters:
    
    coll1 - the first collection, must not be null
    
    coll2 - the first collection, must not be null
    
    Returns:
    
    true iff the intersection of the collections is non-empty
    
    Since:
    
    2.1
    
    See Also:
    
    intersection(java.util.Collection, java.util.Collection)
  - getCardinalityMap
```
public static java.util.Map getCardinalityMap(java.util.Collection coll)
```
    Deprecated.
    
    Returns a Map mapping each unique element in the given Collection to an Integer representing the number of occurrences of that element in the Collection.
    Only those elements present in the collection will appear as keys in the map.
    
    Parameters:
    
    coll - the collection to get the cardinality map for, must not be null
    
    Returns:
    
    the populated cardinality map
  - isSubCollection
```
public static boolean isSubCollection(java.util.Collection a,
                                      java.util.Collection b)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    a - the first (sub?) collection, must not be null
    
    b - the second (super?) collection, must not be null
    
    Returns:
    
    true iff a is a sub-collection of b
    
    See Also:
    
    isProperSubCollection(java.util.Collection, java.util.Collection), Collection.containsAll(java.util.Collection<?>)
  - isProperSubCollection
```
public static boolean isProperSubCollection(java.util.Collection a,
                                            java.util.Collection b)
```
    Deprecated.
    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
    Parameters:
    
    a - the first (sub?) collection, must not be null
    
    b - the second (super?) collection, must not be null
    
    Returns:
    
    true iff a is a proper sub-collection of b
    
    See Also:
    
    isSubCollection(java.util.Collection, java.util.Collection), Collection.containsAll(java.util.Collection<?>)
  - isEqualCollection
```
public static boolean isEqualCollection(java.util.Collection a,
                                        java.util.Collection b)
```
    Deprecated.
    
    Returns true iff the given Collections 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.
    
    Parameters:
    
    a - the first collection, must not be null
    
    b - the second collection, must not be null
    
    Returns:
    
    true iff the collections contain the same elements with the same cardinalities.
  - cardinality
```
public static int cardinality(java.lang.Object obj,
                              java.util.Collection coll)
```
    Deprecated.
    
    Returns the number of occurrences of obj in coll.
    
    Parameters:
    
    obj - the object to find the cardinality of
    
    coll - the collection to search
    
    Returns:
    
    the the number of occurrences of obj in coll
  - find
```
public static java.lang.Object find(java.util.Collection collection,
                                    Predicate predicate)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    collection - the collection to search, may be null
    
    predicate - the predicate to use, may be null
    
    Returns:
    
    the first element of the collection which matches the predicate or null if none could be found
  - forAllDo
```
public static void forAllDo(java.util.Collection collection,
                            Closure closure)
```
    Deprecated.
    
    Executes the given closure on each element in the collection.
    If the input collection or closure is null, there is no change made.
    
    Parameters:
    
    collection - the collection to get the input from, may be null
    
    closure - the closure to perform, may be null
  - filter
```
public static void filter(java.util.Collection collection,
                          Predicate predicate)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    collection - the collection to get the input from, may be null
    
    predicate - the predicate to use as a filter, may be null
  - transform
```
public static void transform(java.util.Collection collection,
                             Transformer transformer)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    collection - the collection to get the input from, may be null
    
    transformer - the transformer to perform, may be null
  - countMatches
```
public static int countMatches(java.util.Collection inputCollection,
                               Predicate predicate)
```
    Deprecated.
    
    Counts the number of elements in the input collection that match the predicate.
    A null collection or predicate matches no elements.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may be null
    
    predicate - the predicate to use, may be null
    
    Returns:
    
    the number of matches for the predicate in the collection
  - exists
```
public static boolean exists(java.util.Collection collection,
                             Predicate predicate)
```
    Deprecated.
    
    Answers true if a predicate is true for at least one element of a collection.
    A null collection or predicate returns false.
    
    Parameters:
    
    collection - the collection to get the input from, may be null
    
    predicate - the predicate to use, may be null
    
    Returns:
    
    true if at least one element of the collection matches the predicate
  - select
```
public static java.util.Collection select(java.util.Collection inputCollection,
                                          Predicate predicate)
```
    Deprecated.
    
    Selects all elements from input collection which match the given predicate into an output collection.
    A null predicate matches no elements.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may not be null
    
    predicate - the predicate to use, may be null
    
    Returns:
    
    the elements matching the predicate (new list)
    
    Throws:
    
    java.lang.NullPointerException - if the input collection is null
  - select
```
public static void select(java.util.Collection inputCollection,
                          Predicate predicate,
                          java.util.Collection outputCollection)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may be null
    
    predicate - the predicate to use, may be null
    
    outputCollection - the collection to output into, may not be null
  - selectRejected
```
public static java.util.Collection selectRejected(java.util.Collection inputCollection,
                                                  Predicate predicate)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may not be null
    
    predicate - the predicate to use, may be null
    
    Returns:
    
    the elements not matching the predicate (new list)
    
    Throws:
    
    java.lang.NullPointerException - if the input collection is null
  - selectRejected
```
public static void selectRejected(java.util.Collection inputCollection,
                                  Predicate predicate,
                                  java.util.Collection outputCollection)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may be null
    
    predicate - the predicate to use, may be null
    
    outputCollection - the collection to output into, may not be null
  - collect
```
public static java.util.Collection collect(java.util.Collection inputCollection,
                                           Transformer transformer)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may not be null
    
    transformer - the transformer to use, may be null
    
    Returns:
    
    the transformed result (new list)
    
    Throws:
    
    java.lang.NullPointerException - if the input collection is null
  - collect
```
public static java.util.Collection collect(java.util.Iterator inputIterator,
                                           Transformer transformer)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputIterator - the iterator to get the input from, may be null
    
    transformer - the transformer to use, may be null
    
    Returns:
    
    the transformed result (new list)
  - collect
```
public static java.util.Collection collect(java.util.Collection inputCollection,
                                           Transformer transformer,
                                           java.util.Collection outputCollection)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputCollection - the collection to get the input from, may be null
    
    transformer - the transformer to use, may be null
    
    outputCollection - the collection to output into, may not be null
    
    Returns:
    
    the outputCollection with the transformed input added
    
    Throws:
    
    java.lang.NullPointerException - if the output collection is null
  - collect
```
public static java.util.Collection collect(java.util.Iterator inputIterator,
                                           Transformer transformer,
                                           java.util.Collection outputCollection)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    inputIterator - the iterator to get the input from, may be null
    
    transformer - the transformer to use, may be null
    
    outputCollection - the collection to output into, may not be null
    
    Returns:
    
    the outputCollection with the transformed input added
    
    Throws:
    
    java.lang.NullPointerException - if the output collection is null
  - addIgnoreNull
```
public static boolean addIgnoreNull(java.util.Collection collection,
                                    java.lang.Object object)
```
    Deprecated.
    
    Adds an element to the collection unless the element is null.
    
    Parameters:
    
    collection - the collection to add to, must not be null
    
    object - the object to add, if null it will not be added
    
    Returns:
    
    true if the collection changed
    
    Throws:
    
    java.lang.NullPointerException - if the collection is null
    
    Since:
    
    Commons Collections 3.2
  - addAll
```
public static void addAll(java.util.Collection collection,
                          java.util.Iterator iterator)
```
    Deprecated.
    
    Adds all elements in the iteration to the given collection.
    
    Parameters:
    
    collection - the collection to add to, must not be null
    
    iterator - the iterator of elements to add, must not be null
    
    Throws:
    
    java.lang.NullPointerException - if the collection or iterator is null
  - addAll
```
public static void addAll(java.util.Collection collection,
                          java.util.Enumeration enumeration)
```
    Deprecated.
    
    Adds all elements in the enumeration to the given collection.
    
    Parameters:
    
    collection - the collection to add to, must not be null
    
    enumeration - the enumeration of elements to add, must not be null
    
    Throws:
    
    java.lang.NullPointerException - if the collection or enumeration is null
  - addAll
```
public static void addAll(java.util.Collection collection,
                          java.lang.Object[] elements)
```
    Deprecated.
    
    Adds all elements in the array to the given collection.
    
    Parameters:
    
    collection - the collection to add to, must not be null
    
    elements - the array of elements to add, must not be null
    
    Throws:
    
    java.lang.NullPointerException - if the collection or array is null
  - index
```
public static java.lang.Object index(java.lang.Object obj,
                                     int idx)
```
    Deprecated.
    use get(Object, int) instead. Will be removed in v4.0
    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.
    Parameters:
    
    obj - the object to get an index of, may be null
    
    idx - the index to get
    
    Throws:
    
    java.lang.IndexOutOfBoundsException
    
    java.lang.ArrayIndexOutOfBoundsException
  - index
```
public static java.lang.Object index(java.lang.Object obj,
                                     java.lang.Object index)
```
    Deprecated.
    use get(Object, int) instead. Will be removed in v4.0
    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.
    Parameters:
    
    obj - the object to get an index of
    
    index - the index to get
    
    Returns:
    
    the object at the specified index
    
    Throws:
    
    java.lang.IndexOutOfBoundsException
    
    java.lang.ArrayIndexOutOfBoundsException
  - get
```
public static java.lang.Object get(java.lang.Object object,
                                   int index)
```
    Deprecated.
    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.
    Parameters:
    
    object - the object to get a value from
    
    index - the index to get
    
    Returns:
    
    the object at the specified index
    
    Throws:
    
    java.lang.IndexOutOfBoundsException - if the index is invalid
    
    java.lang.IllegalArgumentException - if the object type is invalid
  - size
```
public static int size(java.lang.Object object)
```
    Deprecated.
    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
    Parameters:
    
    object - the object to get the size of
    
    Returns:
    
    the size of the specified collection
    
    Throws:
    
    java.lang.IllegalArgumentException - thrown if object is not recognised or null
    
    Since:
    
    Commons Collections 3.1
  - sizeIsEmpty
```
public static boolean sizeIsEmpty(java.lang.Object object)
```
    Deprecated.
    Checks if the specified collection/array/iterator is empty.
    This method can handles objects as follows
    
    Collection - via collection isEmpty
    Map - via map isEmpty
    Array - using array size
    Iterator - via hasNext
    Enumeration - via hasMoreElements
    
    Note: This method is named to avoid clashing with isEmpty(Collection).
    Parameters:
    
    object - the object to get the size of, not null
    
    Returns:
    
    true if empty
    
    Throws:
    
    java.lang.IllegalArgumentException - thrown if object is not recognised or null
    
    Since:
    
    Commons Collections 3.2
  - isEmpty
```
public static boolean isEmpty(java.util.Collection coll)
```
    Deprecated.
    
    Null-safe check if the specified collection is empty.
    Null returns true.
    
    Parameters:
    
    coll - the collection to check, may be null
    
    Returns:
    
    true if empty or null
    
    Since:
    
    Commons Collections 3.2
  - isNotEmpty
```
public static boolean isNotEmpty(java.util.Collection coll)
```
    Deprecated.
    
    Null-safe check if the specified collection is not empty.
    Null returns false.
    
    Parameters:
    
    coll - the collection to check, may be null
    
    Returns:
    
    true if non-null and non-empty
    
    Since:
    
    Commons Collections 3.2
  - reverseArray
```
public static void reverseArray(java.lang.Object[] array)
```
    Deprecated.
    
    Reverses the order of the given array.
    
    Parameters:
    
    array - the array to reverse
  - isFull
```
public static boolean isFull(java.util.Collection coll)
```
    Deprecated.
    
    Returns true if no more elements can be added to the Collection.
    This method uses the 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.
    
    Parameters:
    
    coll - the collection to check
    
    Returns:
    
    true if the BoundedCollection is full
    
    Throws:
    
    java.lang.NullPointerException - if the collection is null
  - maxSize
```
public static int maxSize(java.util.Collection coll)
```
    Deprecated.
    
    Get the maximum number of elements that the Collection can contain.
    This method uses the 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.
    
    Parameters:
    
    coll - the collection to check
    
    Returns:
    
    the maximum size of the BoundedCollection, -1 if no maximum size
    
    Throws:
    
    java.lang.NullPointerException - if the collection is null
  - retainAll
```
public static java.util.Collection retainAll(java.util.Collection collection,
                                             java.util.Collection retain)
```
    Deprecated.
    
    Returns a collection containing all the elements in collection that are also in retain. The cardinality of an element e in the returned collection is the same as the cardinality of e in collection unless retain does not contain e, in which case the cardinality is zero. This method is useful if you do not wish to modify the collection c and thus cannot call c.retainAll(retain);.
    
    Parameters:
    
    collection - the collection whose contents are the target of the #retailAll operation
    
    retain - the collection containing the elements to be retained in the returned collection
    
    Returns:
    
    a Collection containing all the elements of collection that occur at least once in retain.
    
    Throws:
    
    java.lang.NullPointerException - if either parameter is null
    
    Since:
    
    Commons Collections 3.2
  - removeAll
```
public static java.util.Collection removeAll(java.util.Collection collection,
                                             java.util.Collection remove)
```
    Deprecated.
    
    Removes the elements in remove from collection. That is, this method returns a collection containing all the elements in c that are not in remove. The cardinality of an element e in the returned collection is the same as the cardinality of e in collection unless remove contains e, in which case the cardinality is zero. This method is useful if you do not wish to modify the collection c and thus cannot call collection.removeAll(remove);.
    
    Parameters:
    
    collection - the collection from which items are removed (in the returned collection)
    
    remove - the items to be removed from the returned collection
    
    Returns:
    
    a Collection containing all the elements of collection except any elements that also occur in remove.
    
    Throws:
    
    java.lang.NullPointerException - if either parameter is null
    
    Since:
    
    Commons Collections 3.2
  - synchronizedCollection
```
public static java.util.Collection synchronizedCollection(java.util.Collection collection)
```
    Deprecated.
    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.
    Parameters:
    
    collection - the collection to synchronize, must not be null
    
    Returns:
    
    a synchronized collection backed by the given collection
    
    Throws:
    
    java.lang.IllegalArgumentException - if the collection is null
  - unmodifiableCollection
```
public static java.util.Collection unmodifiableCollection(java.util.Collection collection)
```
    Deprecated.
    
    Returns an unmodifiable collection backed by the given collection.
    This method uses the implementation in the decorators subpackage.
    
    Parameters:
    
    collection - the collection to make unmodifiable, must not be null
    
    Returns:
    
    an unmodifiable collection backed by the given collection
    
    Throws:
    
    java.lang.IllegalArgumentException - if the collection is null
  - predicatedCollection
```
public static java.util.Collection predicatedCollection(java.util.Collection collection,
                                                        Predicate predicate)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    collection - the collection to predicate, must not be null
    
    predicate - the predicate for the collection, must not be null
    
    Returns:
    
    a predicated collection backed by the given collection
    
    Throws:
    
    java.lang.IllegalArgumentException - if the Collection is null
  - typedCollection
```
public static java.util.Collection typedCollection(java.util.Collection collection,
                                                   java.lang.Class type)
```
    Deprecated.
    
    Returns a typed collection backed by the given collection.
    Only objects of the specified type can be added to the collection.
    
    Parameters:
    
    collection - the collection to limit to a specific type, must not be null
    
    type - the type of objects which may be added to the collection
    
    Returns:
    
    a typed collection backed by the specified collection
  - transformedCollection
```
public static java.util.Collection transformedCollection(java.util.Collection collection,
                                                         Transformer transformer)
```
    Deprecated.
    
    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.
    
    Parameters:
    
    collection - the collection to predicate, must not be null
    
    transformer - the transformer for the collection, must not be null
    
    Returns:
    
    a transformed collection backed by the given collection
    
    Throws:
    
    java.lang.IllegalArgumentException - if the Collection or Transformer is null

Class CollectionUtils

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

EMPTY_COLLECTION

Constructor Detail

CollectionUtils

Method Detail

union

intersection

disjunction

subtract

containsAny

getCardinalityMap

isSubCollection

isProperSubCollection

isEqualCollection

cardinality

find

forAllDo

filter

transform

countMatches

exists

select

select

selectRejected

selectRejected

collect

collect

collect

collect

addIgnoreNull

addAll

addAll

addAll

index

index

get

size

sizeIsEmpty

isEmpty

isNotEmpty

reverseArray

isFull

maxSize

retainAll

removeAll

synchronizedCollection

unmodifiableCollection

predicatedCollection

typedCollection

transformedCollection