Collections « Collections « Collections

This class consists the methods that operate on or return collections. This class is a member of the Java Collections Framework.

Type	Field	Summary
static List	EMPTY_LIST	The empty list (immutable).
static Map	EMPTY_MAP	The empty map (immutable).
static Set	EMPTY_SET	The empty set (immutable).
static<T> List<T>	emptyList()	Returns the empty list (immutable).
static<K,V> Map<K,V>	emptyMap()	Returns the empty map (immutable).
static<T> Set<T>	emptySet()	Returns the empty set (immutable).

Do binary search

Return	Method	Summary
static<T> int	binarySearch(List<? extends Comparable<? super T>> list, T key)	Searches the specified list for the specified object using the binary search algorithm.
static<T> int	binarySearch(List<? extends T> list, T key, Comparator<? super T> c)	Searches the specified list for the specified object using the binary search algorithm.

Add to a collection

Return	Method	Summary
static<T> boolean	addAll(Collection<? super T> c, T... elements)	Adds all of the specified elements to the specified collection.
static<T> Queue<T>	asLifoQueue(Deque<T> deque)	Returns a view of a Deque as a Last-in-first-out (Lifo) Queue.

Check collections

Return	Method	Summary
static<E> Collection<E>	checkedCollection(Collection<E> c, Class<E> type)	Returns a dynamically typesafe view of the specified collection.
static<E> List<E>	checkedList(List<E> list, Class<E> type)	Returns a dynamically typesafe view of the specified list.
static<K,V> Map<K,V>	checkedMap(Map<K,V> m, Class<K> keyType, Class<V> valueType)	Returns a dynamically typesafe view of the specified map.
static<E> Set<E>	checkedSet(Set<E> s, Class<E> type)	Returns a dynamically typesafe view of the specified set.
static<K,V> SortedMap<K,V>	checkedSortedMap(SortedMap<K,V> m, Class<K> keyType, Class<V> valueType)	Returns a dynamically typesafe view of the specified sorted map.
static<E> SortedSet<E>	checkedSortedSet(SortedSet<E> s, Class<E> type)	Returns a dynamically typesafe view of the specified sorted set.

Copy value to a List

Return	Method	Summary
static<T> void	copy(List<? super T> dest, List<? extends T> src)	Copies all of the elements from one list into another.

Check for common elements

Return	Method	Summary
static boolean	disjoint(Collection<?> c1, Collection<?> c2)	Returns true if the two specified collections have no elements in common.

Get Enumeration from collection, create list from Enumeration

Return	Method	Summary
static<T> Enumeration<T>	enumeration(Collection<T> c)	Returns an enumeration over the specified collection.
static<T> ArrayList<T>	list(Enumeration<T> e)	Returns an array list containing the elements returned by the specified enumeration in the order they are returned by the enumeration.

Fill a list

Return	Method	Summary
static<T> void	fill(List<? super T> list, T obj)	Replaces all of the elements of the specified list with the specified element.

Check for frequency

Return	Method	Summary
static int	frequency(Collection<?> c, Object o)	Returns the number of elements in the specified collection equal to the specified object.

Get the index of sub list

Return	Method	Summary
static int	indexOfSubList(List<?> source, List<?> target)	Returns the starting position of the first occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.
static int	lastIndexOfSubList(List<?> source, List<?> target)	Returns the starting position of the last occurrence of the specified target list within the specified source list, or -1 if there is no such occurrence.

Get the max and min value from a Collection

Return	Method	Summary
static<T extends Object & Comparable<? super T>>T	max(Collection<? extends T> coll)	Returns the maximum element of the given collection, according to the natural ordering of its elements.
static<T> T	max(Collection<? extends T> coll, Comparator<? super T> comp)	Returns the maximum element of the given collection, according to the order induced by the specified comparator.
static<T extends Object & Comparable<? super T>>T	min(Collection<? extends T> coll)	Returns the minimum element of the given collection, according to the natural ordering of its elements.
static<T> T	min(Collection<? extends T> coll, Comparator<? super T> comp)	Returns the minimum element of the given collection, according to the order induced by the specified comparator.

Fill n Copy object to a list

Return	Method	Summary
static<T> List<T>	nCopies(int n, T o)	Returns an immutable list consisting of n copies of the specified object.

Create set from a map

Return	Method	Summary
static<E> Set<E>	newSetFromMap(Map<E,Boolean> map)	Returns a set backed by the specified map.

Replace value in a list

Return	Method	Summary
static<T> boolean	replaceAll(List<T> list, T oldVal, T newVal)	Replaces all occurrences of one specified value in a list with another.

Reverse a list

Return	Method	Summary
static void	reverse(List<?> list)	Reverses the order of the elements in the specified list.

Get comparator in reverse order

Return	Method	Summary
static<T> Comparator<T>	reverseOrder()	Returns a comparator that imposes the reverse of the natural ordering on a collection of objects that implement the Comparable interface.
static<T> Comparator<T>	reverseOrder(Comparator<T> cmp)	Returns a comparator that imposes the reverse ordering of the specified comparator.

Rotate and shuffle a list

Return	Method	Summary
static void	rotate(List<?> list, int distance)	Rotates the elements in the specified list by the specified distance.
static void	shuffle(List<?> list)	Randomly permutes the specified list using a default source of randomness.
static void	shuffle(List<?> list, Random rnd)	Randomly permute the specified list using the specified source of randomness.

Create singleton

Return	Method	Summary
static<T> Set<T>	singleton(T o)	Returns an immutable set containing only the specified object.
static<T> List<T>	singletonList(T o)	Returns an immutable list containing only the specified object.
static<K,V> Map<K,V>	singletonMap(K key, V value)	Returns an immutable map, mapping only the specified key to the specified value.

Sort a list

Return	Method	Summary
static<T extends Comparable<? super T>>void	sort(List<T> list)	Sorts the specified list into ascending order, according to the natural ordering of its elements.
static<T> void	sort(List<T> list, Comparator<? super T> c)	Sorts the specified list according to the order induced by the specified comparator.

Swap element in a list

Return	Method	Summary
static void	swap(List<?> list, int i, int j)	Swaps the elements at the specified positions in the specified list.

Get a synchronized collection

Return	Method	Summary
static<T> Collection<T>	synchronizedCollection(Collection<T> c)	Returns a synchronized (thread-safe) collection backed by the specified collection.
static<T> List<T>	synchronizedList(List<T> list)	Returns a synchronized (thread-safe) list backed by the specified list.
static<K,V> Map<K,V>	synchronizedMap(Map<K,V> m)	Returns a synchronized (thread-safe) map backed by the specified map.
static<T> Set<T>	synchronizedSet(Set<T> s)	Returns a synchronized (thread-safe) set backed by the specified set.
static<K,V> SortedMap<K,V>	synchronizedSortedMap(SortedMap<K,V> m)	Returns a synchronized (thread-safe) sorted map backed by the specified sorted map.
static<T> SortedSet<T>	synchronizedSortedSet(SortedSet<T> s)	Returns a synchronized (thread-safe) sorted set backed by the specified sorted set.

Return an unmodifiable view of collections

Return	Method	Summary
static<T> Collection<T>	unmodifiableCollection(Collection<? extends T> c)	Returns an unmodifiable view of the specified collection.
static<T> List<T>	unmodifiableList(List<? extends T> list)	Returns an unmodifiable view of the specified list.
static<K,V> Map<K,V>	unmodifiableMap(Map<? extends K,? extends V> m)	Returns an unmodifiable view of the specified map.
static<T> Set<T>	unmodifiableSet(Set<? extends T> s)	Returns an unmodifiable view of the specified set.
static<K,V> SortedMap<K,V>	unmodifiableSortedMap(SortedMap<K,? extends V> m)	Returns an unmodifiable view of the specified sorted map.
static<T> SortedSet<T>	unmodifiableSortedSet(SortedSet<T> s)	Returns an unmodifiable view of the specified sorted set.