Collections

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Replace value in a list

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

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

Get comparator in reverse order

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

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

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

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

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

Get a synchronized collection

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

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.

Revised from Open JDK source code

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