com.aoindustries.util

Class AoCollections

java.lang.Object

com.aoindustries.util.AoCollections

public class AoCollections
extends Object

General-purpose collection utilities and constants.

Author:

AO Industries, Inc.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AoCollections.PeekIterator<E> Allows peeking the first element of iteration.

Field Summary

Fields

Modifier and Type	Field and Description
static SortedSet<?>	EMPTY_SORTED_SET

Method Summary

Modifier and Type	Method and Description
static <E> Iterator<E>	emptyIterator() Gets the empty iterator.
static <T> SortedSet<T>	emptySortedSet() Java 1.8: use standard version
static boolean	equals(Collection<?> collection1, Collection<?> collection2) Two collections are considered equal when they are the same size and have the same elements in the same iteration order.
static <E,R extends E> List<R>	filter(List<E> list, Class<R> clazz) Filters a list for all elements of a given class.
static int	hashCode(Iterable<?> iterable) Computes the hashCode of a collection in a manner consistent with AbstractList.
static <T> Collection<T>	optimalUnmodifiableCollection(Collection<T> collection) Gets the optimal implementation for unmodifiable collection.
static <T> List<T>	optimalUnmodifiableList(List<T> list) Gets the optimal implementation for unmodifiable list.
static <K,V> Map<K,V>	optimalUnmodifiableMap(Map<K,V> map) Gets the optimal implementation for unmodifiable map.
static <T> Set<T>	optimalUnmodifiableSet(Set<T> set) Gets the optimal implementation for unmodifiable set.
static <K,V> SortedMap<K,V>	optimalUnmodifiableSortedMap(SortedMap<K,V> sortedMap) Gets the optimal implementation for unmodifiable sorted map.
static <T> SortedSet<T>	optimalUnmodifiableSortedSet(SortedSet<T> sortedSet) Gets the optimal implementation for unmodifiable sorted set.
static <E> AoCollections.PeekIterator<E>	peekIterator(Iterator<? extends E> iter) Wraps the provided iterator, allowing peek of first element.
static <E> Iterator<E>	singletonIterator(E value) Gets an unmodifiable iterator for a single object.
static <T> SortedSet<T>	singletonSortedSet(T o)
static <T> Collection<T>	unmodifiableCopyCollection(Collection<T> collection) Performs defensive shallow copy and returns unmodifiable collection.
static <T> List<T>	unmodifiableCopyList(Collection<T> collection) Performs defensive shallow copy and returns unmodifiable list.
static <K,V> Map<K,V>	unmodifiableCopyMap(Map<K,V> map) Performs defensive shallow copy and returns unmodifiable map.
static <T> Set<T>	unmodifiableCopySet(Collection<T> collection) Performs defensive shallow copy and returns unmodifiable set.
static <K,V> SortedMap<K,V>	unmodifiableCopySortedMap(Map<K,V> map) Performs defensive shallow copy and returns unmodifiable sorted map.
static <T> SortedSet<T>	unmodifiableCopySortedSet(Collection<T> collection) Performs defensive shallow copy and returns unmodifiable sorted set.
static <E> Iterator<E>	unmodifiableIterator(Iterator<E> iter) Wraps an iterator to make it unmodifiable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EMPTY_SORTED_SET

public static final SortedSet<?> EMPTY_SORTED_SET

Method Detail

emptySortedSet

public static final <T> SortedSet<T> emptySortedSet()

Java 1.8: use standard version

singletonSortedSet

public static <T> SortedSet<T> singletonSortedSet(T o)

optimalUnmodifiableCollection

public static <T> Collection<T> optimalUnmodifiableCollection(Collection<T> collection)

Gets the optimal implementation for unmodifiable collection. If the collection is already unmodifiable, returns the same collection. If collection is empty, uses Collections.emptyList. If collection has one element, uses Collections.singletonList. Otherwise, wraps the collection with Collections.unmodifiableCollection.

unmodifiableCopyCollection

public static <T> Collection<T> unmodifiableCopyCollection(Collection<T> collection)

Performs defensive shallow copy and returns unmodifiable collection.

optimalUnmodifiableList

public static <T> List<T> optimalUnmodifiableList(List<T> list)

Gets the optimal implementation for unmodifiable list. If list is empty, uses Collections.emptyList. If list has one element, uses Collections.singletonList. Otherwise, wraps the list with Collections.unmodifiableList, and will also call "trimToSize" if the list is an ArrayList.

See Also:

Collections.emptyList(), Collections.singletonList(java.lang.Object), ArrayList.trimToSize(), Collections.unmodifiableList(java.util.List)

unmodifiableCopyList

public static <T> List<T> unmodifiableCopyList(Collection<T> collection)

Performs defensive shallow copy and returns unmodifiable list.

optimalUnmodifiableSet

public static <T> Set<T> optimalUnmodifiableSet(Set<T> set)

Gets the optimal implementation for unmodifiable set. If set is empty, uses Collections.emptySet. If set has one element, uses Collections.singleton. Otherwise, wraps the set with Collections.unmodifiableSet.

unmodifiableCopySet

public static <T> Set<T> unmodifiableCopySet(Collection<T> collection)

Performs defensive shallow copy and returns unmodifiable set. The iteration order of the original set is maintained.

optimalUnmodifiableSortedSet

public static <T> SortedSet<T> optimalUnmodifiableSortedSet(SortedSet<T> sortedSet)

Gets the optimal implementation for unmodifiable sorted set. If sorted set is empty, uses emptySortedSet. If sorted set has one element, uses singletonSortedSet. Otherwise, wraps the sorted set with Collections.unmodifiableSortedSet.

unmodifiableCopySortedSet

public static <T> SortedSet<T> unmodifiableCopySortedSet(Collection<T> collection)

Performs defensive shallow copy and returns unmodifiable sorted set.

optimalUnmodifiableMap

public static <K,V> Map<K,V> optimalUnmodifiableMap(Map<K,V> map)

Gets the optimal implementation for unmodifiable map. If map is empty, uses Collections.emptyMap. If map has one element, uses Collections.singletonMap. Otherwise, wraps the map with Collections.unmodifiableMap.

unmodifiableCopyMap

public static <K,V> Map<K,V> unmodifiableCopyMap(Map<K,V> map)

Performs defensive shallow copy and returns unmodifiable map. The iteration order of the original set is maintained.

optimalUnmodifiableSortedMap

public static <K,V> SortedMap<K,V> optimalUnmodifiableSortedMap(SortedMap<K,V> sortedMap)

Gets the optimal implementation for unmodifiable sorted map. If sorted map is empty, uses emptySortedMap. If sorted map has one element, uses singletonSortedMap. Otherwise, wraps the sorted map with Collections.unmodifiableSortedMap.

unmodifiableCopySortedMap

public static <K,V> SortedMap<K,V> unmodifiableCopySortedMap(Map<K,V> map)

Performs defensive shallow copy and returns unmodifiable sorted map.

emptyIterator

public static <E> Iterator<E> emptyIterator()

Gets the empty iterator.

singletonIterator

public static <E> Iterator<E> singletonIterator(E value)

Gets an unmodifiable iterator for a single object.

unmodifiableIterator

public static <E> Iterator<E> unmodifiableIterator(Iterator<E> iter)

Wraps an iterator to make it unmodifiable.

peekIterator

public static <E> AoCollections.PeekIterator<E> peekIterator(Iterator<? extends E> iter)

Wraps the provided iterator, allowing peek of first element. Does not support null elements.

equals

public static boolean equals(Collection<?> collection1,
                             Collection<?> collection2)

Two collections are considered equal when they are the same size and have the same elements in the same iteration order. If both collections are null they are also considered equal.

hashCode

public static int hashCode(Iterable<?> iterable)

Computes the hashCode of a collection in a manner consistent with AbstractList.

See Also:

AbstractList.hashCode()

filter

public static <E,R extends E> List<R> filter(List<E> list,
                                             Class<R> clazz)

Filters a list for all elements of a given class.