Module java.base
Package java.util
Contains the collections framework, some internationalization support classes,
a service loader, properties, random number generation, string parsing
and scanning classes, base64 encoding and decoding, a bit array, and
several miscellaneous utility classes. This package also contains
legacy collection classes and legacy date and time classes.
Java Collections Framework
For an overview, API outline, and design rationale, please see:
For a tutorial and programming guide with examples of use of the collections framework, please see:
- Since:
- 1.0
-
Interface Summary Interface Description Collection<E> The root interface in the collection hierarchy.Comparator<T> A comparison function, which imposes a total ordering on some collection of objects.Deque<E> A linear collection that supports element insertion and removal at both ends.Enumeration<E> An object that implements the Enumeration interface generates a series of elements, one at a time.EventListener A tagging interface that all event listener interfaces must extend.Formattable TheFormattableinterface must be implemented by any class that needs to perform custom formatting using the's'conversion specifier ofFormatter.Iterator<E> An iterator over a collection.List<E> An ordered collection (also known as a sequence).ListIterator<E> An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator's current position in the list.Map<K,V> An object that maps keys to values.Map.Entry<K,V> A map entry (key-value pair).NavigableMap<K,V> ASortedMapextended with navigation methods returning the closest matches for given search targets.NavigableSet<E> ASortedSetextended with navigation methods reporting closest matches for given search targets.Observer Deprecated. This interface has been deprecated.PrimitiveIterator<T,T_CONS> A base type for primitive specializations ofIterator.PrimitiveIterator.OfDouble An Iterator specialized fordoublevalues.PrimitiveIterator.OfInt An Iterator specialized forintvalues.PrimitiveIterator.OfLong An Iterator specialized forlongvalues.Queue<E> A collection designed for holding elements prior to processing.RandomAccess Marker interface used byListimplementations to indicate that they support fast (generally constant time) random access.ServiceLoader.Provider<S> Represents a service provider located byServiceLoader.Set<E> A collection that contains no duplicate elements.SortedMap<K,V> AMapthat further provides a total ordering on its keys.SortedSet<E> ASetthat further provides a total ordering on its elements.Spliterator<T> An object for traversing and partitioning elements of a source.Spliterator.OfDouble A Spliterator specialized fordoublevalues.Spliterator.OfInt A Spliterator specialized forintvalues.Spliterator.OfLong A Spliterator specialized forlongvalues.Spliterator.OfPrimitive<T,T_CONS,T_SPLITR extends Spliterator.OfPrimitive<T,T_CONS,T_SPLITR>> A Spliterator specialized for primitive values. -
Class Summary Class Description AbstractCollection<E> This class provides a skeletal implementation of theCollectioninterface, to minimize the effort required to implement this interface.AbstractList<E> This class provides a skeletal implementation of theListinterface to minimize the effort required to implement this interface backed by a "random access" data store (such as an array).AbstractMap<K,V> This class provides a skeletal implementation of theMapinterface, to minimize the effort required to implement this interface.AbstractMap.SimpleEntry<K,V> An Entry maintaining a key and a value.AbstractMap.SimpleImmutableEntry<K,V> An Entry maintaining an immutable key and value.AbstractQueue<E> This class provides skeletal implementations of someQueueoperations.AbstractSequentialList<E> This class provides a skeletal implementation of theListinterface to minimize the effort required to implement this interface backed by a "sequential access" data store (such as a linked list).AbstractSet<E> This class provides a skeletal implementation of theSetinterface to minimize the effort required to implement this interface.ArrayDeque<E> Resizable-array implementation of theDequeinterface.ArrayList<E> Resizable-array implementation of theListinterface.Arrays This class contains various methods for manipulating arrays (such as sorting and searching).Base64 This class consists exclusively of static methods for obtaining encoders and decoders for the Base64 encoding scheme.Base64.Decoder This class implements a decoder for decoding byte data using the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.Base64.Encoder This class implements an encoder for encoding byte data using the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.BitSet This class implements a vector of bits that grows as needed.Calendar TheCalendarclass is an abstract class that provides methods for converting between a specific instant in time and a set ofcalendar fieldssuch asYEAR,MONTH,DAY_OF_MONTH,HOUR, and so on, and for manipulating the calendar fields, such as getting the date of the next week.Calendar.Builder Calendar.Builderis used for creating aCalendarfrom various date-time parameters.Collections This class consists exclusively of static methods that operate on or return collections.Currency Represents a currency.Date The classDaterepresents a specific instant in time, with millisecond precision.Dictionary<K,V> TheDictionaryclass is the abstract parent of any class, such asHashtable, which maps keys to values.DoubleSummaryStatistics A state object for collecting statistics such as count, min, max, sum, and average.EnumMap<K extends Enum<K>,V> A specializedMapimplementation for use with enum type keys.EnumSet<E extends Enum<E>> A specializedSetimplementation for use with enum types.EventListenerProxy<T extends EventListener> An abstract wrapper class for anEventListenerclass which associates a set of additional parameters with the listener.EventObject The root class from which all event state objects shall be derived.FormattableFlags FormattableFlags are passed to theFormattable.formatTo()method and modify the output format for Formattables.Formatter An interpreter for printf-style format strings.GregorianCalendar GregorianCalendaris a concrete subclass ofCalendarand provides the standard calendar system used by most of the world.HashMap<K,V> Hash table based implementation of theMapinterface.HashSet<E> This class implements theSetinterface, backed by a hash table (actually aHashMapinstance).Hashtable<K,V> This class implements a hash table, which maps keys to values.IdentityHashMap<K,V> This class implements theMapinterface with a hash table, using reference-equality in place of object-equality when comparing keys (and values).IntSummaryStatistics A state object for collecting statistics such as count, min, max, sum, and average.LinkedHashMap<K,V> Hash table and linked list implementation of theMapinterface, with predictable iteration order.LinkedHashSet<E> Hash table and linked list implementation of theSetinterface, with predictable iteration order.LinkedList<E> Doubly-linked list implementation of theListandDequeinterfaces.ListResourceBundle ListResourceBundleis an abstract subclass ofResourceBundlethat manages resources for a locale in a convenient and easy to use list.Locale ALocaleobject represents a specific geographical, political, or cultural region.Locale.Builder Builderis used to build instances ofLocalefrom values configured by the setters.Locale.LanguageRange This class expresses a Language Range defined in RFC 4647 Matching of Language Tags.LongSummaryStatistics A state object for collecting statistics such as count, min, max, sum, and average.Objects This class consists ofstaticutility methods for operating on objects, or checking certain conditions before operation.Observable Deprecated. This class and theObserverinterface have been deprecated.Optional<T> A container object which may or may not contain a non-nullvalue.OptionalDouble A container object which may or may not contain adoublevalue.OptionalInt A container object which may or may not contain anintvalue.OptionalLong A container object which may or may not contain alongvalue.PriorityQueue<E> An unbounded priority queue based on a priority heap.Properties ThePropertiesclass represents a persistent set of properties.PropertyPermission This class is for property permissions.PropertyResourceBundle PropertyResourceBundleis a concrete subclass ofResourceBundlethat manages resources for a locale using a set of static strings from a property file.Random An instance of this class is used to generate a stream of pseudorandom numbers.ResourceBundle Resource bundles contain locale-specific objects.ResourceBundle.Control ResourceBundle.Controldefines a set of callback methods that are invoked by theResourceBundle.getBundlefactory methods during the bundle loading process.Scanner A simple text scanner which can parse primitive types and strings using regular expressions.ServiceLoader<S> A facility to load implementations of a service.SimpleTimeZone SimpleTimeZoneis a concrete subclass ofTimeZonethat represents a time zone for use with a Gregorian calendar.Spliterators Static classes and methods for operating on or creating instances ofSpliteratorand its primitive specializationsSpliterator.OfInt,Spliterator.OfLong, andSpliterator.OfDouble.Spliterators.AbstractDoubleSpliterator An abstractSpliterator.OfDoublethat implementstrySplitto permit limited parallelism.Spliterators.AbstractIntSpliterator An abstractSpliterator.OfIntthat implementstrySplitto permit limited parallelism.Spliterators.AbstractLongSpliterator An abstractSpliterator.OfLongthat implementstrySplitto permit limited parallelism.Spliterators.AbstractSpliterator<T> An abstractSpliteratorthat implementstrySplitto permit limited parallelism.SplittableRandom A generator of uniform pseudorandom values applicable for use in (among other contexts) isolated parallel computations that may generate subtasks.Stack<E> TheStackclass represents a last-in-first-out (LIFO) stack of objects.StringJoiner StringJoineris used to construct a sequence of characters separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix.StringTokenizer The string tokenizer class allows an application to break a string into tokens.Timer A facility for threads to schedule tasks for future execution in a background thread.TimerTask A task that can be scheduled for one-time or repeated execution by aTimer.TimeZone TimeZonerepresents a time zone offset, and also figures out daylight savings.TreeMap<K,V> A Red-Black tree basedNavigableMapimplementation.TreeSet<E> ANavigableSetimplementation based on aTreeMap.UUID A class that represents an immutable universally unique identifier (UUID).Vector<E> TheVectorclass implements a growable array of objects.WeakHashMap<K,V> Hash table based implementation of theMapinterface, with weak keys. -
Enum Summary Enum Description Formatter.BigDecimalLayoutForm Enum forBigDecimalformatting.Locale.Category Enum for locale categories.Locale.FilteringMode This enum provides constants to select a filtering mode for locale matching.Locale.IsoCountryCode Enum for specifying the type defined in ISO 3166. -
Exception Summary Exception Description ConcurrentModificationException This exception may be thrown by methods that have detected concurrent modification of an object when such modification is not permissible.DuplicateFormatFlagsException Unchecked exception thrown when duplicate flags are provided in the format specifier.EmptyStackException Thrown by methods in theStackclass to indicate that the stack is empty.FormatFlagsConversionMismatchException Unchecked exception thrown when a conversion and flag are incompatible.FormatterClosedException Unchecked exception thrown when the formatter has been closed.IllegalFormatCodePointException Unchecked exception thrown when a character with an invalid Unicode code point as defined byCharacter.isValidCodePoint(int)is passed to theFormatter.IllegalFormatConversionException Unchecked exception thrown when the argument corresponding to the format specifier is of an incompatible type.IllegalFormatException Unchecked exception thrown when a format string contains an illegal syntax or a format specifier that is incompatible with the given arguments.IllegalFormatFlagsException Unchecked exception thrown when an illegal combination flags is given.IllegalFormatPrecisionException Unchecked exception thrown when the precision is a negative value other than-1, the conversion does not support a precision, or the value is otherwise unsupported.IllegalFormatWidthException Unchecked exception thrown when the format width is a negative value other than-1or is otherwise unsupported.IllformedLocaleException Thrown by methods inLocaleandLocale.Builderto indicate that an argument is not a well-formed BCP 47 tag.InputMismatchException Thrown by aScannerto indicate that the token retrieved does not match the pattern for the expected type, or that the token is out of range for the expected type.InvalidPropertiesFormatException Thrown to indicate that an operation could not complete because the input did not conform to the appropriate XML document type for a collection of properties, as per thePropertiesspecification.MissingFormatArgumentException Unchecked exception thrown when there is a format specifier which does not have a corresponding argument or if an argument index refers to an argument that does not exist.MissingFormatWidthException Unchecked exception thrown when the format width is required.MissingResourceException Signals that a resource is missing.NoSuchElementException Thrown by various accessor methods to indicate that the element being requested does not exist.TooManyListenersException TheTooManyListenersExceptionException is used as part of the Java Event model to annotate and implement a unicast special case of a multicast Event Source.UnknownFormatConversionException Unchecked exception thrown when an unknown conversion is given.UnknownFormatFlagsException Unchecked exception thrown when an unknown flag is given. -
Error Summary Error Description ServiceConfigurationError Error thrown when something goes wrong while locating, loading, or instantiating a service provider.