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 | 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 | The |
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> | A |
NavigableSet<E> | A |
Observer | Deprecated. This interface has been deprecated. |
PrimitiveIterator<T,T_CONS> | A base type for primitive specializations of |
PrimitiveIterator.OfDouble | An Iterator specialized for |
PrimitiveIterator.OfInt | An Iterator specialized for |
PrimitiveIterator.OfLong | An Iterator specialized for |
Queue<E> | A collection designed for holding elements prior to processing. |
RandomAccess | Marker interface used by |
ServiceLoader.Provider<S> | Represents a service provider located by |
Set<E> | A collection that contains no duplicate elements. |
SortedMap<K,V> | A |
SortedSet<E> | A |
Spliterator<T> | An object for traversing and partitioning elements of a source. |
Spliterator.OfDouble | A Spliterator specialized for |
Spliterator.OfInt | A Spliterator specialized for |
Spliterator.OfLong | A Spliterator specialized for |
Spliterator.OfPrimitive<T,T_CONS,T_SPLITR extends Spliterator.OfPrimitive<T,T_CONS,T_SPLITR>> | A Spliterator specialized for primitive values. |
Class | Description |
---|---|
AbstractCollection<E> | This class provides a skeletal implementation of the |
AbstractList<E> | This class provides a skeletal implementation of the |
AbstractMap<K,V> | This class provides a skeletal implementation of the |
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 some |
AbstractSequentialList<E> | This class provides a skeletal implementation of the |
AbstractSet<E> | This class provides a skeletal implementation of the |
ArrayDeque<E> | Resizable-array implementation of the |
ArrayList<E> | Resizable-array implementation of the |
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 | The |
Calendar.Builder |
|
Collections | This class consists exclusively of static methods that operate on or return collections. |
Currency | Represents a currency. |
Date | The class |
Dictionary<K,V> | The |
DoubleSummaryStatistics | A state object for collecting statistics such as count, min, max, sum, and average. |
EnumMap<K extends Enum<K>,V> | A specialized |
EnumSet<E extends Enum<E>> | A specialized |
EventListenerProxy<T extends EventListener> | An abstract wrapper class for an |
EventObject | The root class from which all event state objects shall be derived. |
FormattableFlags | FormattableFlags are passed to the |
Formatter | An interpreter for printf-style format strings. |
GregorianCalendar |
|
HashMap<K,V> | Hash table based implementation of the |
HashSet<E> | This class implements the |
Hashtable<K,V> | This class implements a hash table, which maps keys to values. |
IdentityHashMap<K,V> | This class implements the |
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 the |
LinkedHashSet<E> | Hash table and linked list implementation of the |
LinkedList<E> | Doubly-linked list implementation of the |
ListResourceBundle |
|
Locale | A |
Locale.Builder |
|
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 of |
Observable | Deprecated. This class and the Observer interface have been deprecated. |
Optional<T> | A container object which may or may not contain a non- |
OptionalDouble | A container object which may or may not contain a |
OptionalInt | A container object which may or may not contain an |
OptionalLong | A container object which may or may not contain a |
PriorityQueue<E> | An unbounded priority queue based on a priority heap. |
Properties | The |
PropertyPermission | This class is for property permissions. |
PropertyResourceBundle |
|
Random | An instance of this class is used to generate a stream of pseudorandom numbers. |
ResourceBundle | Resource bundles contain locale-specific objects. |
ResourceBundle.Control |
|
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 |
|
Spliterators | Static classes and methods for operating on or creating instances of |
Spliterators.AbstractDoubleSpliterator | An abstract |
Spliterators.AbstractIntSpliterator | An abstract |
Spliterators.AbstractLongSpliterator | An abstract |
Spliterators.AbstractSpliterator<T> | An abstract |
SplittableRandom | A generator of uniform pseudorandom values applicable for use in (among other contexts) isolated parallel computations that may generate subtasks. |
Stack<E> | The |
StringJoiner |
|
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 a |
TimeZone |
|
TreeMap<K,V> | A Red-Black tree based |
TreeSet<E> | A |
UUID | A class that represents an immutable universally unique identifier (UUID). |
Vector<E> | The |
WeakHashMap<K,V> | Hash table based implementation of the |
Enum | Description |
---|---|
Formatter.BigDecimalLayoutForm | Enum for |
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 | 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 the |
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 by |
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 |
IllegalFormatWidthException | Unchecked exception thrown when the format width is a negative value other than |
IllformedLocaleException | Thrown by methods in |
InputMismatchException | Thrown by a |
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 the |
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 | The |
UnknownFormatConversionException | Unchecked exception thrown when an unknown conversion is given. |
UnknownFormatFlagsException | Unchecked exception thrown when an unknown flag is given. |
Error | Description |
---|---|
ServiceConfigurationError | Error thrown when something goes wrong while locating, loading, or instantiating a service provider. |