java.util

Class Collections

java.lang.Object

java.util.Collections

public class Collections
extends Object

Utility methods that operate on collections. [Sun docs]

Field Summary

Fields

Modifier and Type	Field and Description
static List	EMPTY_LIST
static Map	EMPTY_MAP
static Set	EMPTY_SET

Constructor Summary

Constructors

Constructor and Description
Collections()

Method Summary

Modifier and Type	Method and Description
static <T> boolean	addAll(Collection<? super T> c, T... a)
static <T> int	binarySearch(List<? extends Comparable<? super T>> sortedList, T key) Perform a binary search on a sorted List, using natural ordering.
static <T> int	binarySearch(List<? extends T> sortedList, T key, Comparator<? super T> comparator) Perform a binary search on a sorted List, using a user-specified comparison function.
static <T> void	copy(List<? super T> dest, List<? extends T> src)
static boolean	disjoint(Collection<?> c1, Collection<?> c2)
static <T> List<T>	emptyList()
static <K,V> Map<K,V>	emptyMap()
static <T> Set<T>	emptySet()
static <T> Enumeration<T>	enumeration(Collection<T> c)
static <T> void	fill(List<? super T> list, T obj)
static int	frequency(Collection<?> c, Object o)
static <T> ArrayList<T>	list(Enumeration<T> e)
static <T extends Object & Comparable<? super T>> T	max(Collection<? extends T> coll)
static <T> T	max(Collection<? extends T> coll, Comparator<? super T> comp)
static <T extends Object & Comparable<? super T>> T	min(Collection<? extends T> coll)
static <T> T	min(Collection<? extends T> coll, Comparator<? super T> comp)
static <T> List<T>	nCopies(int n, T o)
static <T> boolean	replaceAll(List<T> list, T oldVal, T newVal)
static <T> void	reverse(List<T> l)
static <T> Comparator<T>	reverseOrder()
static <T> Comparator<T>	reverseOrder(Comparator<T> cmp)
static <T> Set<T>	singleton(T o)
static <T> List<T>	singletonList(T o)
static <K,V> Map<K,V>	singletonMap(K key, V value)
static <T> void	sort(List<T> target)
static <T> void	sort(List<T> target, Comparator<? super T> c)
static void	swap(List<?> list, int i, int j)
static <T> Collection<T>	unmodifiableCollection(Collection<? extends T> coll)
static <T> List<T>	unmodifiableList(List<? extends T> list)
static <K,V> Map<K,V>	unmodifiableMap(Map<? extends K,? extends V> map)
static <T> Set<T>	unmodifiableSet(Set<? extends T> set)
static <K,V> SortedMap<K,V>	unmodifiableSortedMap(SortedMap<K,? extends V> map)
static <T> SortedSet<T>	unmodifiableSortedSet(SortedSet<? extends T> set)

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, toString

Field Detail

EMPTY_LIST

public static final List EMPTY_LIST

EMPTY_MAP

public static final Map EMPTY_MAP

EMPTY_SET

public static final Set EMPTY_SET

Constructor Detail

Collections

public Collections()

Method Detail

addAll

public static <T> boolean addAll(Collection<? super T> c,
                                 T... a)

binarySearch

public static <T> int binarySearch(List<? extends Comparable<? super T>> sortedList,
                                   T key)

Perform a binary search on a sorted List, using natural ordering.

Note: The GWT implementation differs from the JDK implementation in that it does not do an iterator-based binary search for Lists that do not implement RandomAccess.

Parameters:

sortedList - object array to search

key - value to search for

Returns:

the index of an element with a matching value, or a negative number which is the index of the next larger value (or just past the end of the array if the searched value is larger than all elements in the array) minus 1 (to ensure error returns are negative)

Throws:

ClassCastException - if key is not comparable to sortedList's elements.

binarySearch

public static <T> int binarySearch(List<? extends T> sortedList,
                                   T key,
                                   Comparator<? super T> comparator)

Perform a binary search on a sorted List, using a user-specified comparison function.

Note: The GWT implementation differs from the JDK implementation in that it does not do an iterator-based binary search for Lists that do not implement RandomAccess.

Parameters:

sortedList - List to search

key - value to search for

comparator - comparision function, null indicates natural ordering should be used.

Returns:

the index of an element with a matching value, or a negative number which is the index of the next larger value (or just past the end of the array if the searched value is larger than all elements in the array) minus 1 (to ensure error returns are negative)

Throws:

ClassCastException - if key and sortedList's elements cannot be compared by comparator.

copy

public static <T> void copy(List<? super T> dest,
                            List<? extends T> src)

disjoint

public static boolean disjoint(Collection<?> c1,
                               Collection<?> c2)

emptyList

public static <T> List<T> emptyList()

emptyMap

public static <K,V> Map<K,V> emptyMap()

emptySet

public static <T> Set<T> emptySet()

enumeration

public static <T> Enumeration<T> enumeration(Collection<T> c)

fill

public static <T> void fill(List<? super T> list,
                            T obj)

frequency

public static int frequency(Collection<?> c,
                            Object o)

list

public static <T> ArrayList<T> list(Enumeration<T> e)

max

public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll)

max

public static <T> T max(Collection<? extends T> coll,
                        Comparator<? super T> comp)

min

public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll)

min

public static <T> T min(Collection<? extends T> coll,
                        Comparator<? super T> comp)

nCopies

public static <T> List<T> nCopies(int n,
                                  T o)

replaceAll

public static <T> boolean replaceAll(List<T> list,
                                     T oldVal,
                                     T newVal)

reverse

public static <T> void reverse(List<T> l)

reverseOrder

public static <T> Comparator<T> reverseOrder()

reverseOrder

public static <T> Comparator<T> reverseOrder(Comparator<T> cmp)

singleton

public static <T> Set<T> singleton(T o)

singletonList

public static <T> List<T> singletonList(T o)

singletonMap

public static <K,V> Map<K,V> singletonMap(K key,
                                          V value)

sort

public static <T> void sort(List<T> target)

sort

public static <T> void sort(List<T> target,
                            Comparator<? super T> c)

swap

public static void swap(List<?> list,
                        int i,
                        int j)

unmodifiableCollection

public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> coll)

unmodifiableList

public static <T> List<T> unmodifiableList(List<? extends T> list)

unmodifiableMap

public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K,? extends V> map)

unmodifiableSet

public static <T> Set<T> unmodifiableSet(Set<? extends T> set)

unmodifiableSortedMap

public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K,? extends V> map)

unmodifiableSortedSet

public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<? extends T> set)