public abstract class

CollectionUtils

extends Object
java.lang.Object
   ↳ org.springframework.util.CollectionUtils

Class Overview

Miscellaneous collection utility methods. Mainly for internal use within the framework.

Summary

Public Constructors
CollectionUtils()
Public Methods
static List arrayToList(Object source)
Convert the supplied array into a List.
static boolean contains(Enumeration enumeration, Object element)
Check whether the given Enumeration contains the given element.
static boolean contains(Iterator iterator, Object element)
Check whether the given Iterator contains the given element.
static boolean containsAny(Collection source, Collection candidates)
Return true if any element in 'candidates' is contained in 'source'; otherwise returns false.
static boolean containsInstance(Collection collection, Object element)
Check whether the given Collection contains the given element instance.
static Class<?> findCommonElementType(Collection collection)
Find the common element type of the given Collection, if any.
static Object findFirstMatch(Collection source, Collection candidates)
Return the first element in 'candidates' that is contained in 'source'.
static <T> T findValueOfType(Collection<?> collection, Class<T> type)
Find a single value of the given type in the given Collection.
static Object findValueOfType(Collection<?> collection, 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.
static boolean hasUniqueObject(Collection collection)
Determine whether the given Collection only contains a single unique object.
static boolean isEmpty(Map map)
Return true if the supplied Map is null or empty.
static boolean isEmpty(Collection collection)
Return true if the supplied Collection is null or empty.
static void mergeArrayIntoCollection(Object array, Collection collection)
Merge the given array into the given Collection.
static void mergePropertiesIntoMap(Properties props, Map map)
Merge the given Properties instance into the given Map, copying all properties (key-value pairs) over.
static <A, E extends A> A[] toArray(Enumeration<E> enumeration, A[] array)
Marshal the elements from the given enumeration into an array of the given type.
static <E> Iterator<E> toIterator(Enumeration<E> enumeration)
Adapt an enumeration to an iterator.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public CollectionUtils ()

Also: SpringCore

Public Methods

public static List arrayToList (Object source)

Also: SpringCore

Convert the supplied array into a List. A primitive array gets converted into a List of the appropriate wrapper type.

A null source value will be converted to an empty List.

Parameters
source the (potentially primitive) array
Returns
  • the converted List result
See Also

public static boolean contains (Enumeration enumeration, Object element)

Also: SpringCore

Check whether the given Enumeration contains the given element.

Parameters
enumeration the Enumeration to check
element the element to look for
Returns
  • true if found, false else

public static boolean contains (Iterator iterator, Object element)

Also: SpringCore

Check whether the given Iterator contains the given element.

Parameters
iterator the Iterator to check
element the element to look for
Returns
  • true if found, false else

public static boolean containsAny (Collection source, Collection candidates)

Also: SpringCore

Return true if any element in 'candidates' is contained in 'source'; otherwise returns false.

Parameters
source the source Collection
candidates the candidates to search for
Returns
  • whether any of the candidates has been found

public static boolean containsInstance (Collection collection, Object element)

Also: SpringCore

Check whether the given Collection contains the given element instance.

Enforces the given instance to be present, rather than returning true for an equal element as well.

Parameters
collection the Collection to check
element the element to look for
Returns
  • true if found, false else

public static Class<?> findCommonElementType (Collection collection)

Also: SpringCore

Find the common element type of the given Collection, if any.

Parameters
collection the Collection to check
Returns
  • the common element type, or null if no clear common type has been found (or the collection was empty)

public static Object findFirstMatch (Collection source, Collection candidates)

Also: SpringCore

Return the first element in 'candidates' that is contained in 'source'. If no element in 'candidates' is present in 'source' returns null. Iteration order is Collection implementation specific.

Parameters
source the source Collection
candidates the candidates to search for
Returns
  • the first present object, or null if not found

public static T findValueOfType (Collection<?> collection, Class<T> type)

Also: SpringCore

Find a single value of the given type in the given Collection.

Parameters
collection the Collection to search
type the type to look for
Returns
  • a value of the given type found if there is a clear match, or null if none or more than one such value found

public static Object findValueOfType (Collection<?> collection, Class[]<?> types)

Also: SpringCore

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.

Parameters
collection the collection to search
types the types to look for, in prioritized order
Returns
  • a value of one of the given types found if there is a clear match, or null if none or more than one such value found

public static boolean hasUniqueObject (Collection collection)

Also: SpringCore

Determine whether the given Collection only contains a single unique object.

Parameters
collection the Collection to check
Returns
  • true if the collection contains a single reference or multiple references to the same instance, false else

public static boolean isEmpty (Map map)

Also: SpringCore

Return true if the supplied Map is null or empty. Otherwise, return false.

Parameters
map the Map to check
Returns
  • whether the given Map is empty

public static boolean isEmpty (Collection collection)

Also: SpringCore

Return true if the supplied Collection is null or empty. Otherwise, return false.

Parameters
collection the Collection to check
Returns
  • whether the given Collection is empty

public static void mergeArrayIntoCollection (Object array, Collection collection)

Also: SpringCore

Merge the given array into the given Collection.

Parameters
array the array to merge (may be null)
collection the target Collection to merge the array into

public static void mergePropertiesIntoMap (Properties props, Map map)

Also: SpringCore

Merge the given Properties instance into the given Map, copying all properties (key-value pairs) over.

Uses Properties.propertyNames() to even catch default properties linked into the original Properties instance.

Parameters
props the Properties instance to merge (may be null)
map the target Map to merge the properties into

public static A[] toArray (Enumeration<E> enumeration, A[] array)

Also: SpringCore

Marshal the elements from the given enumeration into an array of the given type. Enumeration elements must be assignable to the type of the given array. The array returned will be a different instance than the array given.

public static Iterator<E> toIterator (Enumeration<E> enumeration)

Also: SpringCore

Adapt an enumeration to an iterator.

Parameters
enumeration the enumeration
Returns
  • the iterator