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java.lang.Objectorg.springframework.util.CollectionUtils
public abstract class CollectionUtils
Miscellaneous collection utility methods. Mainly for internal use within the framework.
Constructor Summary | |
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CollectionUtils()
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Method Summary | ||
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static java.util.List<?> |
arrayToList(java.lang.Object source)
Convert the supplied array into a List. |
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static boolean |
contains(java.util.Enumeration<?> enumeration,
java.lang.Object element)
Check whether the given Enumeration contains the given element. |
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static boolean |
contains(java.util.Iterator<?> iterator,
java.lang.Object element)
Check whether the given Iterator contains the given element. |
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static boolean |
containsAny(java.util.Collection<?> source,
java.util.Collection<?> candidates)
Return true if any element in 'candidates ' is contained in 'source ';
otherwise returns false . |
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static boolean |
containsInstance(java.util.Collection<?> collection,
java.lang.Object element)
Check whether the given Collection contains the given element instance. |
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static java.lang.Class<?> |
findCommonElementType(java.util.Collection<?> collection)
Find the common element type of the given Collection, if any. |
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static java.lang.Object |
findFirstMatch(java.util.Collection<?> source,
java.util.Collection<?> candidates)
Return the first element in ' candidates ' that is contained in 'source '. |
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static java.lang.Object |
findValueOfType(java.util.Collection<?> collection,
java.lang.Class<?>[] types)
Find a single value of one of the given types in the given Collection: searching the Collection for a value of the first type, then searching for a value of the second type, etc. |
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static
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findValueOfType(java.util.Collection<?> collection,
java.lang.Class<T> type)
Find a single value of the given type in the given Collection. |
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static boolean |
hasUniqueObject(java.util.Collection<?> collection)
Determine whether the given Collection only contains a single unique object. |
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static boolean |
isEmpty(java.util.Collection<?> collection)
Return true if the supplied Collection is null or empty. |
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static boolean |
isEmpty(java.util.Map<?,?> map)
Return true if the supplied Map is null or empty. |
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static void |
mergeArrayIntoCollection(java.lang.Object array,
java.util.Collection<java.lang.Object> collection)
Merge the given array into the given Collection. |
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static void |
mergePropertiesIntoMap(java.util.Properties props,
java.util.Map<java.lang.String,java.lang.Object> map)
Merge the given Properties instance into the given Map, copying all properties (key-value pairs) over. |
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static
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toArray(java.util.Enumeration<E> enumeration,
A[] array)
Marshal the elements from the given enumeration into an array of the given type. |
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static
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toIterator(java.util.Enumeration<E> enumeration)
Adapt an enumeration to an iterator. |
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static
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toMultiValueMap(java.util.Map<K,java.util.List<V>> map)
Adapts a Map<K, List<V>> to an MultiValueMap<K,V> . |
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static
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unmodifiableMultiValueMap(MultiValueMap<? extends K,? extends V> map)
Returns an unmodifiable view of the specified multi-value map. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public CollectionUtils()
Method Detail |
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public static boolean isEmpty(java.util.Collection<?> collection)
true
if the supplied Collection is null
or empty. Otherwise, return
false
.
collection
- the Collection to check
public static boolean isEmpty(java.util.Map<?,?> map)
true
if the supplied Map is null
or empty. Otherwise, return false
.
map
- the Map to check
public static java.util.List<?> arrayToList(java.lang.Object source)
A null
source value will be converted to an empty List.
source
- the (potentially primitive) array
ObjectUtils.toObjectArray(Object)
public static void mergeArrayIntoCollection(java.lang.Object array, java.util.Collection<java.lang.Object> collection)
array
- the array to merge (may be null
)collection
- the target Collection to merge the array intopublic static void mergePropertiesIntoMap(java.util.Properties props, java.util.Map<java.lang.String,java.lang.Object> map)
Uses Properties.propertyNames()
to even catch default properties linked into the original Properties
instance.
props
- the Properties instance to merge (may be null
)map
- the target Map to merge the properties intopublic static boolean contains(java.util.Iterator<?> iterator, java.lang.Object element)
iterator
- the Iterator to checkelement
- the element to look for
true
if found, false
elsepublic static boolean contains(java.util.Enumeration<?> enumeration, java.lang.Object element)
enumeration
- the Enumeration to checkelement
- the element to look for
true
if found, false
elsepublic static boolean containsInstance(java.util.Collection<?> collection, java.lang.Object element)
Enforces the given instance to be present, rather than returning true
for an equal element as well.
collection
- the Collection to checkelement
- the element to look for
true
if found, false
elsepublic static boolean containsAny(java.util.Collection<?> source, java.util.Collection<?> candidates)
true
if any element in 'candidates
' is contained in 'source
';
otherwise returns false
.
source
- the source Collectioncandidates
- the candidates to search for
public static java.lang.Object findFirstMatch(java.util.Collection<?> source, java.util.Collection<?> candidates)
candidates
' that is contained in 'source
'. If no element
in 'candidates
' is present in 'source
' returns null
. Iteration order is
Collection
implementation specific.
source
- the source Collectioncandidates
- the candidates to search for
null
if not foundpublic static <T> T findValueOfType(java.util.Collection<?> collection, java.lang.Class<T> type)
collection
- the Collection to searchtype
- the type to look for
null
if none or more than one
such value foundpublic static java.lang.Object findValueOfType(java.util.Collection<?> collection, java.lang.Class<?>[] types)
collection
- the collection to searchtypes
- the types to look for, in prioritized order
null
if none or more
than one such value foundpublic static boolean hasUniqueObject(java.util.Collection<?> collection)
collection
- the Collection to check
true
if the collection contains a single reference or multiple references to the same
instance, false
elsepublic static java.lang.Class<?> findCommonElementType(java.util.Collection<?> collection)
collection
- the Collection to check
null
if no clear common type has been found (or the collection
was empty)public static <A,E extends A> A[] toArray(java.util.Enumeration<E> enumeration, A[] array)
public static <E> java.util.Iterator<E> toIterator(java.util.Enumeration<E> enumeration)
enumeration
- the enumeration
public static <K,V> MultiValueMap<K,V> toMultiValueMap(java.util.Map<K,java.util.List<V>> map)
Map<K, List<V>>
to an MultiValueMap<K,V>
.
map
- the map
public static <K,V> MultiValueMap<K,V> unmodifiableMultiValueMap(MultiValueMap<? extends K,? extends V> map)
map
- the map for which an unmodifiable view is to be returned.
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