java.util.Collections

public class Collections
extends Object

Collections contains static methods which operate on Collection classes.

Since:: 1.2

Field Summary

Fields
Modifier and Type	Field	Description
`static List`	`EMPTY_LIST`	An empty immutable instance of `List`.
`static Map`	`EMPTY_MAP`	An empty immutable instance of `Map`.
`static Set`	`EMPTY_SET`	An empty immutable instance of `Set`.

Method Summary

Modifier and Type	Method	Description
`static <T> boolean`	`addAll(Collection<? super T> c, T... a)`	Adds all the specified elements to the specified collection.
`static <T> Queue<T>`	`asLifoQueue(Deque<T> deque)`	Returns a last-in, first-out queue as a view of `deque`.
`static <T> int`	`binarySearch(List<? extends Comparable<? super T>> list, T object)`	Performs a binary search for the specified element in the specified sorted list.
`static <T> int`	`binarySearch(List<? extends T> list, T object, Comparator<? super T> comparator)`	Performs a binary search for the specified element in the specified sorted list using the specified comparator.
`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.
`static <T> void`	`copy(List<? super T> destination, List<? extends T> source)`	Copies the elements from the source list to the destination list.
`static boolean`	`disjoint(Collection<?> c1, Collection<?> c2)`	Returns whether the specified collections have no elements in common.
`static <T> Enumeration<T>`	`emptyEnumeration()`	Returns an enumeration containing no elements.
`static <T> Iterator<T>`	`emptyIterator()`	Returns an iterator containing no elements.
`static <T> List<T>`	`emptyList()`	Returns a type-safe empty, immutable `List`.
`static <T> ListIterator<T>`	`emptyListIterator()`	Returns a list iterator containing no elements.
`static <K, V> Map<K,V>`	`emptyMap()`	Returns a type-safe empty, immutable `Map`.
`static <T> Set<T>`	`emptySet()`	Returns a type-safe empty, immutable `Set`.
`static <T> Enumeration<T>`	`enumeration(Collection<T> collection)`	Returns an `Enumeration` on the specified collection.
`static <T> void`	`fill(List<? super T> list, T object)`	Fills the specified list with the specified element.
`static int`	`frequency(Collection<?> c, Object o)`	Returns the number of elements in the `Collection` that match the `Object` passed.
`static int`	`indexOfSubList(List<?> list, List<?> sublist)`	Searches the `list` for `sublist` and returns the beginning index of the first occurrence.
`static int`	`lastIndexOfSubList(List<?> list, List<?> sublist)`	Searches the `list` for `sublist` and returns the beginning index of the last occurrence.
`static <T> ArrayList<T>`	`list(Enumeration<T> enumeration)`	Returns an `ArrayList` with all the elements in the `enumeration`.
`static <T extends Object & Comparable<? super T>> T`	`max(Collection<? extends T> collection)`	Searches the specified collection for the maximum element.
`static <T> T`	`max(Collection<? extends T> collection, Comparator<? super T> comparator)`	Searches the specified collection for the maximum element using the specified comparator.
`static <T extends Object & Comparable<? super T>> T`	`min(Collection<? extends T> collection)`	Searches the specified collection for the minimum element.
`static <T> T`	`min(Collection<? extends T> collection, Comparator<? super T> comparator)`	Searches the specified collection for the minimum element using the specified comparator.
`static <T> List<T>`	`nCopies(int length, T object)`	Returns a list containing the specified number of the specified element.
`static <E> Set<E>`	`newSetFromMap(Map<E,Boolean> map)`	Returns a set backed by `map`.
`static <T> boolean`	`replaceAll(List<T> list, T obj, T obj2)`	Replaces all occurrences of Object `obj` in `list` with `newObj`.
`static void`	`reverse(List<?> list)`	Modifies the specified `List` by reversing the order of the elements.
`static <T> Comparator<T>`	`reverseOrder()`	A comparator which reverses the natural order of the elements.
`static <T> Comparator<T>`	`reverseOrder(Comparator<T> c)`	Returns a `Comparator` that reverses the order of the `Comparator` passed.
`static void`	`rotate(List<?> lst, int dist)`	Rotates the elements in `list` by the distance `dist`
`static int`	`roundUpToPowerOfTwo(int i)`	Returns the smallest power of two >= its argument, with several caveats: If the argument is negative but not Integer.MIN_VALUE, the method returns zero.
`static int`	`secondaryHash(Object key)`	Computes a hash code and applies a supplemental hash function to defend against poor quality hash functions.
`static int`	`secondaryIdentityHash(Object key)`	Computes an identity hash code and applies a supplemental hash function to defend against poor quality hash functions.
`static void`	`shuffle(List<?> list)`	Moves every element of the list to a random new position in the list.
`static void`	`shuffle(List<?> list, Random random)`	Moves every element of the list to a random new position in the list using the specified random number generator.
`static <E> Set<E>`	`singleton(E object)`	Returns a set containing the specified element.
`static <E> List<E>`	`singletonList(E object)`	Returns a list containing the specified element.
`static <K, V> Map<K,V>`	`singletonMap(K key, V value)`	Returns a Map containing the specified key and value.
`static <T extends Comparable<? super T>> void`	`sort(List<T> list)`	Sorts the given list in ascending natural order.
`static <T> void`	`sort(List<T> list, Comparator<? super T> comparator)`	Sorts the given list using the given comparator.
`static void`	`swap(List<?> list, int index1, int index2)`	Swaps the elements of list `list` at indices `index1` and `index2`.
`static <T> Collection<T>`	`synchronizedCollection(Collection<T> collection)`	Returns a wrapper on the specified collection which synchronizes all access to the collection.
`static <T> List<T>`	`synchronizedList(List<T> list)`	Returns a wrapper on the specified List which synchronizes all access to the List.
`static <K, V> Map<K,V>`	`synchronizedMap(Map<K,V> map)`	Returns a wrapper on the specified map which synchronizes all access to the map.
`static <E> Set<E>`	`synchronizedSet(Set<E> set)`	Returns a wrapper on the specified set which synchronizes all access to the set.
`static <K, V> SortedMap<K,V>`	`synchronizedSortedMap(SortedMap<K,V> map)`	Returns a wrapper on the specified sorted map which synchronizes all access to the sorted map.
`static <E> SortedSet<E>`	`synchronizedSortedSet(SortedSet<E> set)`	Returns a wrapper on the specified sorted set which synchronizes all access to the sorted set.
`static <E> Collection<E>`	`unmodifiableCollection(Collection<? extends E> collection)`	Returns a wrapper on the specified collection which throws an `UnsupportedOperationException` whenever an attempt is made to modify the collection.
`static <E> List<E>`	`unmodifiableList(List<? extends E> list)`	Returns a wrapper on the specified list which throws an `UnsupportedOperationException` whenever an attempt is made to modify the list.
`static <K, V> Map<K,V>`	`unmodifiableMap(Map<? extends K,? extends V> map)`	Returns a wrapper on the specified map which throws an `UnsupportedOperationException` whenever an attempt is made to modify the map.
`static <E> Set<E>`	`unmodifiableSet(Set<? extends E> set)`	Returns a wrapper on the specified set which throws an `UnsupportedOperationException` whenever an attempt is made to modify the set.
`static <K, V> SortedMap<K,V>`	`unmodifiableSortedMap(SortedMap<K,? extends V> map)`	Returns a wrapper on the specified sorted map which throws an `UnsupportedOperationException` whenever an attempt is made to modify the sorted map.
`static <E> SortedSet<E>`	`unmodifiableSortedSet(SortedSet<E> set)`	Returns a wrapper on the specified sorted set which throws an `UnsupportedOperationException` whenever an attempt is made to modify the sorted set.

Methods inherited from class java.lang.Object

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

Field Details
- EMPTY_LIST
  
  public static final List EMPTY_LIST
  
  An empty immutable instance of List.
- EMPTY_SET
  
  public static final Set EMPTY_SET
  
  An empty immutable instance of Set.
- EMPTY_MAP
  
  public static final Map EMPTY_MAP
  
  An empty immutable instance of Map.
Method Details
- binarySearch
  
  public static <T> int binarySearch(List<? extends Comparable<? super T>> list, T object)
  
  Performs a binary search for the specified element in the specified sorted list. The list needs to be already sorted in natural sorting order. Searching in an unsorted array has an undefined result. It's also undefined which element is found if there are multiple occurrences of the same element.
  
  Parameters:
  
  list - the sorted list to search.
  
  object - the element to find.
  
  Returns:
  
  the non-negative index of the element, or a negative index which is the -index - 1 where the element would be inserted
  
  Throws:
  
  ClassCastException - if an element in the List or the search element does not implement Comparable, or cannot be compared to each other.
- binarySearch
  
  public static <T> int binarySearch(List<? extends T> list, T object, Comparator<? super T> comparator)
  
  Performs a binary search for the specified element in the specified sorted list using the specified comparator. The list needs to be already sorted according to the comparator passed. Searching in an unsorted array has an undefined result. It's also undefined which element is found if there are multiple occurrences of the same element.
  
  Parameters:
  
  list - the sorted List to search.
  
  object - the element to find.
  
  comparator - the comparator. If the comparator is null then the search uses the objects' natural ordering.
  
  Returns:
  
  the non-negative index of the element, or a negative index which is the -index - 1 where the element would be inserted.
  
  Throws:
  
  ClassCastException - when an element in the list and the searched element cannot be compared to each other using the comparator.
- copy
  
  public static <T> void copy(List<? super T> destination, List<? extends T> source)
  
  Copies the elements from the source list to the destination list. At the end both lists will have the same objects at the same index. If the destination array is larger than the source list, the elements in the destination list with index >= source.size() will be unchanged.
  
  Parameters:
  
  destination - the list whose elements are set from the source list.
  
  source - the list with the elements to be copied into the destination.
  
  Throws:
  
  IndexOutOfBoundsException - when the destination list is smaller than the source list.
  
  UnsupportedOperationException - when replacing an element in the destination list is not supported.
- enumeration
  
  public static <T> Enumeration<T> enumeration(Collection<T> collection)
  
  Returns an Enumeration on the specified collection.
  
  Parameters:
  
  collection - the collection to enumerate.
  
  Returns:
  
  an Enumeration.
- fill
  
  public static <T> void fill(List<? super T> list, T object)
  
  Fills the specified list with the specified element.
  
  Parameters:
  
  list - the list to fill.
  
  object - the element to fill the list with.
  
  Throws:
  
  UnsupportedOperationException - when replacing an element in the List is not supported.
- max
  
  public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> collection)
  
  Searches the specified collection for the maximum element.
  
  Parameters:
  
  collection - the collection to search.
  
  Returns:
  
  the maximum element in the Collection.
  
  Throws:
  
  ClassCastException - when an element in the collection does not implement Comparable or elements cannot be compared to each other.
- max
  
  public static <T> T max(Collection<? extends T> collection, Comparator<? super T> comparator)
  
  Searches the specified collection for the maximum element using the specified comparator.
  
  Parameters:
  
  collection - the collection to search.
  
  comparator - the comparator.
  
  Returns:
  
  the maximum element in the Collection.
  
  Throws:
  
  ClassCastException - when elements in the collection cannot be compared to each other using the Comparator.
- min
  
  public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> collection)
  
  Searches the specified collection for the minimum element.
  
  Parameters:
  
  collection - the collection to search.
  
  Returns:
  
  the minimum element in the collection.
  
  Throws:
  
  ClassCastException - when an element in the collection does not implement Comparable or elements cannot be compared to each other.
- min
  
  public static <T> T min(Collection<? extends T> collection, Comparator<? super T> comparator)
  
  Searches the specified collection for the minimum element using the specified comparator.
  
  Parameters:
  
  collection - the collection to search.
  
  comparator - the comparator.
  
  Returns:
  
  the minimum element in the collection.
  
  Throws:
  
  ClassCastException - when elements in the collection cannot be compared to each other using the Comparator.
- nCopies
  
  public static <T> List<T> nCopies(int length, T object)
  
  Returns a list containing the specified number of the specified element. The list cannot be modified. The list is serializable.
  
  Parameters:
  
  length - the size of the returned list.
  
  object - the element to be added length times to a list.
  
  Returns:
  
  a list containing length copies of the element.
  
  Throws:
  
  IllegalArgumentException - when length < 0.
- reverse
  
  public static void reverse(List<?> list)
  
  Modifies the specified List by reversing the order of the elements.
  
  Parameters:
  
  list - the list to reverse.
  
  Throws:
  
  UnsupportedOperationException - when replacing an element in the List is not supported.
- reverseOrder
  
  public static <T> Comparator<T> reverseOrder()
  
  A comparator which reverses the natural order of the elements. The Comparator that's returned is Serializable.
  
  Returns:
  
  a Comparator instance.
- reverseOrder
  
  public static <T> Comparator<T> reverseOrder(Comparator<T> c)
  
  Returns a Comparator that reverses the order of the Comparator passed. If the Comparator passed is null, then this method is equivalent to reverseOrder().
  The Comparator that's returned is Serializable if the Comparator passed is serializable or null.
  
  Parameters:
  
  c - the Comparator to reverse or null.
  
  Returns:
  
  a Comparator instance.
  
  Since:
  
  1.5
- shuffle
  
  public static void shuffle(List<?> list)
  
  Moves every element of the list to a random new position in the list.
  
  Parameters:
  
  list - the List to shuffle.
  
  Throws:
  
  UnsupportedOperationException - when replacing an element in the List is not supported.
- shuffle
  
  public static void shuffle(List<?> list, Random random)
  
  Moves every element of the list to a random new position in the list using the specified random number generator.
  
  Parameters:
  
  list - the list to shuffle.
  
  random - the random number generator.
  
  Throws:
  
  UnsupportedOperationException - when replacing an element in the list is not supported.
- singleton
  
  public static <E> Set<E> singleton(E object)
  
  Returns a set containing the specified element. The set cannot be modified. The set is serializable.
  
  Parameters:
  
  object - the element.
  
  Returns:
  
  a set containing the element.
- singletonList
  
  public static <E> List<E> singletonList(E object)
  
  Returns a list containing the specified element. The list cannot be modified. The list is serializable.
  
  Parameters:
  
  object - the element.
  
  Returns:
  
  a list containing the element.
- singletonMap
  
  public static <K, V> Map<K,V> singletonMap(K key, V value)
  
  Returns a Map containing the specified key and value. The map cannot be modified. The map is serializable.
  
  Parameters:
  
  key - the key.
  
  value - the value.
  
  Returns:
  
  a Map containing the key and value.
- sort
  
  public static <T extends Comparable<? super T>> void sort(List<T> list)
  
  Sorts the given list in ascending natural order. The algorithm is stable which means equal elements don't get reordered.
  
  Throws:
  
  ClassCastException - if any element does not implement Comparable, or if compareTo throws for any pair of elements.
- sort
  
  public static <T> void sort(List<T> list, Comparator<? super T> comparator)
  
  Sorts the given list using the given comparator. The algorithm is stable which means equal elements don't get reordered.
  
  Throws:
  
  ClassCastException - if any element does not implement Comparable, or if compareTo throws for any pair of elements.
- swap
  
  public static void swap(List<?> list, int index1, int index2)
  
  Swaps the elements of list list at indices index1 and index2.
  
  Parameters:
  
  list - the list to manipulate.
  
  index1 - position of the first element to swap with the element in index2.
  
  index2 - position of the other element.
  
  Throws:
  
  IndexOutOfBoundsException - if index1 or index2 is out of range of this list.
  
  Since:
  
  1.4
- replaceAll
  
  public static <T> boolean replaceAll(List<T> list, T obj, T obj2)
  
  Replaces all occurrences of Object obj in list with newObj. If the obj is null, then all occurrences of null are replaced with newObj.
  
  Parameters:
  
  list - the list to modify.
  
  obj - the object to find and replace occurrences of.
  
  obj2 - the object to replace all occurrences of obj in list.
  
  Returns:
  
  true, if at least one occurrence of obj has been found in list.
  
  Throws:
  
  UnsupportedOperationException - if the list does not support setting elements.
- rotate
  
  public static void rotate(List<?> lst, int dist)
  
  Rotates the elements in list by the distance dist
  e.g. for a given list with elements [1, 2, 3, 4, 5, 6, 7, 8, 9, 0], calling rotate(list, 3) or rotate(list, -7) would modify the list to look like this: [8, 9, 0, 1, 2, 3, 4, 5, 6, 7]
  
  Parameters:
  
  lst - the list whose elements are to be rotated.
  
  dist - is the distance the list is rotated. This can be any valid integer. Negative values rotate the list backwards.
- indexOfSubList
  
  public static int indexOfSubList(List<?> list, List<?> sublist)
  
  Searches the list for sublist and returns the beginning index of the first occurrence.
  -1 is returned if the sublist does not exist in list.
  
  Parameters:
  
  list - the List to search sublist in.
  
  sublist - the List to search in list.
  
  Returns:
  
  the beginning index of the first occurrence of sublist in list, or -1.
- lastIndexOfSubList
  
  public static int lastIndexOfSubList(List<?> list, List<?> sublist)
  
  Searches the list for sublist and returns the beginning index of the last occurrence.
  -1 is returned if the sublist does not exist in list.
  
  Parameters:
  
  list - the list to search sublist in.
  
  sublist - the list to search in list.
  
  Returns:
  
  the beginning index of the last occurrence of sublist in list, or -1.
- list
  
  public static <T> ArrayList<T> list(Enumeration<T> enumeration)
  
  Returns an ArrayList with all the elements in the enumeration. The elements in the returned ArrayList are in the same order as in the enumeration.
  
  Parameters:
  
  enumeration - the source Enumeration.
  
  Returns:
  
  an ArrayList from enumeration.
- synchronizedCollection
  
  public static <T> Collection<T> synchronizedCollection(Collection<T> collection)
  
  Returns a wrapper on the specified collection which synchronizes all access to the collection.
  
  Parameters:
  
  collection - the Collection to wrap in a synchronized collection.
  
  Returns:
  
  a synchronized Collection.
- synchronizedList
  
  public static <T> List<T> synchronizedList(List<T> list)
  
  Returns a wrapper on the specified List which synchronizes all access to the List.
  
  Parameters:
  
  list - the List to wrap in a synchronized list.
  
  Returns:
  
  a synchronized List.
- synchronizedMap
  
  public static <K, V> Map<K,V> synchronizedMap(Map<K,V> map)
  
  Returns a wrapper on the specified map which synchronizes all access to the map.
  
  Parameters:
  
  map - the map to wrap in a synchronized map.
  
  Returns:
  
  a synchronized Map.
- synchronizedSet
  
  public static <E> Set<E> synchronizedSet(Set<E> set)
  
  Returns a wrapper on the specified set which synchronizes all access to the set.
  
  Parameters:
  
  set - the set to wrap in a synchronized set.
  
  Returns:
  
  a synchronized set.
- synchronizedSortedMap
  
  public static <K, V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> map)
  
  Returns a wrapper on the specified sorted map which synchronizes all access to the sorted map.
  
  Parameters:
  
  map - the sorted map to wrap in a synchronized sorted map.
  
  Returns:
  
  a synchronized sorted map.
- synchronizedSortedSet
  
  public static <E> SortedSet<E> synchronizedSortedSet(SortedSet<E> set)
  
  Returns a wrapper on the specified sorted set which synchronizes all access to the sorted set.
  
  Parameters:
  
  set - the sorted set to wrap in a synchronized sorted set.
  
  Returns:
  
  a synchronized sorted set.
- unmodifiableCollection
  
  public static <E> Collection<E> unmodifiableCollection(Collection<? extends E> collection)
  
  Returns a wrapper on the specified collection which throws an UnsupportedOperationException whenever an attempt is made to modify the collection.
  
  Parameters:
  
  collection - the collection to wrap in an unmodifiable collection.
  
  Returns:
  
  an unmodifiable collection.
- unmodifiableList
  
  public static <E> List<E> unmodifiableList(List<? extends E> list)
  
  Returns a wrapper on the specified list which throws an UnsupportedOperationException whenever an attempt is made to modify the list.
  
  Parameters:
  
  list - the list to wrap in an unmodifiable list.
  
  Returns:
  
  an unmodifiable List.
- unmodifiableMap
  
  public static <K, V> Map<K,V> unmodifiableMap(Map<? extends K,? extends V> map)
  
  Returns a wrapper on the specified map which throws an UnsupportedOperationException whenever an attempt is made to modify the map.
  
  Parameters:
  
  map - the map to wrap in an unmodifiable map.
  
  Returns:
  
  a unmodifiable map.
- unmodifiableSet
  
  public static <E> Set<E> unmodifiableSet(Set<? extends E> set)
  
  Returns a wrapper on the specified set which throws an UnsupportedOperationException whenever an attempt is made to modify the set.
  
  Parameters:
  
  set - the set to wrap in an unmodifiable set.
  
  Returns:
  
  a unmodifiable set
- unmodifiableSortedMap
  
  public static <K, V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K,? extends V> map)
  
  Returns a wrapper on the specified sorted map which throws an UnsupportedOperationException whenever an attempt is made to modify the sorted map.
  
  Parameters:
  
  map - the sorted map to wrap in an unmodifiable sorted map.
  
  Returns:
  
  a unmodifiable sorted map
- unmodifiableSortedSet
  
  public static <E> SortedSet<E> unmodifiableSortedSet(SortedSet<E> set)
  
  Returns a wrapper on the specified sorted set which throws an UnsupportedOperationException whenever an attempt is made to modify the sorted set.
  
  Parameters:
  
  set - the sorted set to wrap in an unmodifiable sorted set.
  
  Returns:
  
  a unmodifiable sorted set.
- frequency
  
  public static int frequency(Collection<?> c, Object o)
  
  Returns the number of elements in the Collection that match the Object passed. If the Object is null, then the number of null elements is returned.
  
  Parameters:
  
  c - the Collection to search.
  
  o - the Object to search for.
  
  Returns:
  
  the number of matching elements.
  
  Throws:
  
  NullPointerException - if the Collection parameter is null.
  
  Since:
  
  1.5
- emptyList
  
  public static final <T> List<T> emptyList()
  
  Returns a type-safe empty, immutable List.
  
  Returns:
  
  an empty List.
  
  Since:
  
  1.5
  
  See Also:
  
  EMPTY_LIST
- emptySet
  
  public static final <T> Set<T> emptySet()
  
  Returns a type-safe empty, immutable Set.
  
  Returns:
  
  an empty Set.
  
  Since:
  
  1.5
  
  See Also:
  
  EMPTY_SET
- emptyMap
  
  public static final <K, V> Map<K,V> emptyMap()
  
  Returns a type-safe empty, immutable Map.
  
  Returns:
  
  an empty Map.
  
  Since:
  
  1.5
  
  See Also:
  
  EMPTY_MAP
- emptyEnumeration
  
  public static <T> Enumeration<T> emptyEnumeration()
  
  Returns an enumeration containing no elements.
  
  Since:
  
  1.7
- emptyIterator
  
  public static <T> Iterator<T> emptyIterator()
  
  Returns an iterator containing no elements.
  
  Since:
  
  1.7
- emptyListIterator
  
  public static <T> ListIterator<T> emptyListIterator()
  
  Returns a list iterator containing no elements.
  
  Since:
  
  1.7
- checkedCollection
  
  public static <E> Collection<E> checkedCollection(Collection<E> c, Class<E> type)
  
  Returns a dynamically typesafe view of the specified collection. Trying to insert an element of the wrong type into this collection throws a ClassCastException. At creation time the types in c are not checked for correct type.
  
  Parameters:
  
  c - the collection to be wrapped in a typesafe collection.
  
  type - the type of the elements permitted to insert.
  
  Returns:
  
  a typesafe collection.
- checkedMap
  
  public 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. Trying to insert an element of the wrong type into this map throws a ClassCastException. At creation time the types in m are not checked for correct type.
  
  Parameters:
  
  m - the map to be wrapped in a typesafe map.
  
  keyType - the type of the keys permitted to insert.
  
  valueType - the type of the values permitted to insert.
  
  Returns:
  
  a typesafe map.
- checkedList
  
  public static <E> List<E> checkedList(List<E> list, Class<E> type)
  
  Returns a dynamically typesafe view of the specified list. Trying to insert an element of the wrong type into this list throws a ClassCastException. At creation time the types in list are not checked for correct type.
  
  Parameters:
  
  list - the list to be wrapped in a typesafe list.
  
  type - the type of the elements permitted to insert.
  
  Returns:
  
  a typesafe list.
- checkedSet
  
  public static <E> Set<E> checkedSet(Set<E> s, Class<E> type)
  
  Returns a dynamically typesafe view of the specified set. Trying to insert an element of the wrong type into this set throws a ClassCastException. At creation time the types in s are not checked for correct type.
  
  Parameters:
  
  s - the set to be wrapped in a typesafe set.
  
  type - the type of the elements permitted to insert.
  
  Returns:
  
  a typesafe set.
- checkedSortedMap
  
  public 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. Trying to insert an element of the wrong type into this sorted map throws a ClassCastException. At creation time the types in m are not checked for correct type.
  
  Parameters:
  
  m - the sorted map to be wrapped in a typesafe sorted map.
  
  keyType - the type of the keys permitted to insert.
  
  valueType - the type of the values permitted to insert.
  
  Returns:
  
  a typesafe sorted map.
- checkedSortedSet
  
  public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s, Class<E> type)
  
  Returns a dynamically typesafe view of the specified sorted set. Trying to insert an element of the wrong type into this sorted set throws a ClassCastException. At creation time the types in s are not checked for correct type.
  
  Parameters:
  
  s - the sorted set to be wrapped in a typesafe sorted set.
  
  type - the type of the elements permitted to insert.
  
  Returns:
  
  a typesafe sorted set.
- addAll
  
  @SafeVarargs public static <T> boolean addAll(Collection<? super T> c, T... a)
  
  Adds all the specified elements to the specified collection.
  
  Parameters:
  
  c - the collection the elements are to be inserted into.
  
  a - the elements to insert.
  
  Returns:
  
  true if the collection changed during insertion.
  
  Throws:
  
  UnsupportedOperationException - when the method is not supported.
  
  NullPointerException - when c or a is null, or a contains one or more null elements and c doesn't support null elements.
  
  IllegalArgumentException - if at least one of the elements can't be inserted into the collection.
- disjoint
  
  public static boolean disjoint(Collection<?> c1, Collection<?> c2)
  
  Returns whether the specified collections have no elements in common.
  
  Parameters:
  
  c1 - the first collection.
  
  c2 - the second collection.
  
  Returns:
  
  true if the collections have no elements in common, false otherwise.
  
  Throws:
  
  NullPointerException - if one of the collections is null.
- newSetFromMap
  
  public static <E> Set<E> newSetFromMap(Map<E,Boolean> map)
  
  Returns a set backed by map.
  
  Throws:
  
  IllegalArgumentException - if the map is not empty
  
  Since:
  
  1.6
- asLifoQueue
  
  public static <T> Queue<T> asLifoQueue(Deque<T> deque)
  
  Returns a last-in, first-out queue as a view of deque.
  
  Since:
  
  1.6
- secondaryHash
  
  public static int secondaryHash(Object key)
  
  Computes a hash code and applies a supplemental hash function to defend against poor quality hash functions. This is critical because HashMap uses power-of-two length hash tables, that otherwise encounter collisions for hash codes that do not differ in lower or upper bits. Routine taken from java.util.concurrent.ConcurrentHashMap.hash(int).
- secondaryIdentityHash
  
  public static int secondaryIdentityHash(Object key)
  
  Computes an identity hash code and applies a supplemental hash function to defend against poor quality hash functions. This is critical because identity hash codes are currently implemented as object addresses, which will have been aligned by the underlying memory allocator causing all hash codes to have the same bottom bits.
- roundUpToPowerOfTwo
  
  public static int roundUpToPowerOfTwo(int i)
  
  Returns the smallest power of two >= its argument, with several caveats: If the argument is negative but not Integer.MIN_VALUE, the method returns zero. If the argument is > 2^30 or equal to Integer.MIN_VALUE, the method returns Integer.MIN_VALUE. If the argument is zero, the method returns zero.

Class Collections

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Details

EMPTY_LIST

EMPTY_SET

EMPTY_MAP

Method Details

binarySearch

binarySearch

copy

enumeration

fill

max

max

min

min

nCopies

reverse

reverseOrder

reverseOrder

shuffle

shuffle

singleton

singletonList

singletonMap

sort

sort

swap

replaceAll

rotate

indexOfSubList

lastIndexOfSubList

list

synchronizedCollection

synchronizedList

synchronizedMap

synchronizedSet

synchronizedSortedMap

synchronizedSortedSet

unmodifiableCollection

unmodifiableList

unmodifiableMap

unmodifiableSet

unmodifiableSortedMap

unmodifiableSortedSet

frequency

emptyList

emptySet

emptyMap

emptyEnumeration

emptyIterator

emptyListIterator

checkedCollection

checkedMap

checkedList

checkedSet

checkedSortedMap

checkedSortedSet

addAll

disjoint

newSetFromMap

asLifoQueue

secondaryHash

secondaryIdentityHash

roundUpToPowerOfTwo