Package org.apache.lucene.util

Some utility classes.

See: Description

Interface Summary

Interface	Description
Accountable	An object whose RAM usage can be computed.
Attribute	Base interface for attributes.
AttributeReflector	This interface is used to reflect contents of AttributeSource or AttributeImpl.
Bits	Interface for Bitset-like structures.
BytesRefArray.IndexedBytesRefIterator	An extension of BytesRefIterator that allows retrieving the index of the current element
BytesRefIterator	A simple iterator interface for BytesRef iteration.
IOSupplier<T>	This is a result supplier that is allowed to throw an IOException.
IOUtils.IOConsumer<T>	An IO operation with a single input.
IOUtils.IOFunction<T,R>	A Function that may throw an IOException
NamedSPILoader.NamedSPI	Interface to support NamedSPILoader.lookup(String) by name.
RollingBuffer.Resettable	Implement to reset an instance

Class Summary

Class	Description
Accountables	Helper methods for constructing nested resource descriptions and debugging RAM usage.
ArrayUtil	Methods for manipulating arrays.
AttributeFactory	An AttributeFactory creates instances of AttributeImpls.
AttributeFactory.StaticImplementationAttributeFactory<A extends AttributeImpl>	Expert: AttributeFactory returning an instance of the given clazz for the attributes it implements.
AttributeImpl	Base class for Attributes that can be added to a AttributeSource.
AttributeSource	An AttributeSource contains a list of different AttributeImpls, and methods to add and get them.
AttributeSource.State	This class holds the state of an AttributeSource.
BitDocIdSet	Implementation of the DocIdSet interface on top of a BitSet.
Bits.MatchAllBits	Bits impl of the specified length with all bits set.
Bits.MatchNoBits	Bits impl of the specified length with no bits set.
BitSet	Base implementation for a bit set.
BitSetIterator	A DocIdSetIterator which iterates over set bits in a bit set.
BitUtil	A variety of high efficiency bit twiddling routines.
ByteBlockPool	Class that Posting and PostingVector use to write byte streams into shared fixed-size byte[] arrays.
ByteBlockPool.Allocator	Abstract class for allocating and freeing byte blocks.
ByteBlockPool.DirectAllocator	A simple ByteBlockPool.Allocator that never recycles.
ByteBlockPool.DirectTrackingAllocator	A simple ByteBlockPool.Allocator that never recycles, but tracks how much total RAM is in use.
BytesRef	Represents byte[], as a slice (offset + length) into an existing byte[].
BytesRefArray	A simple append only random-access BytesRef array that stores full copies of the appended bytes in a ByteBlockPool.
BytesRefArray.SortState	Used to iterate the elements of an array in a given order.
BytesRefBuilder	A builder for BytesRef instances.
BytesRefComparator	Specialized BytesRef comparator that FixedLengthBytesRefArray.iterator(Comparator) has optimizations for.
BytesRefHash	BytesRefHash is a special purpose hash-map like data-structure optimized for BytesRef instances.
BytesRefHash.BytesStartArray	Manages allocation of the per-term addresses.
BytesRefHash.DirectBytesStartArray	A simple BytesRefHash.BytesStartArray that tracks memory allocation using a private Counter instance.
CharsRef	Represents char[], as a slice (offset + length) into an existing char[].
CharsRefBuilder	A builder for CharsRef instances.
CloseableThreadLocal<T>	Java's builtin ThreadLocal has a serious flaw: it can take an arbitrarily long amount of time to dereference the things you had stored in it, even once the ThreadLocal instance itself is no longer referenced.
CollectionUtil	Methods for manipulating (sorting) collections.
CommandLineUtil	Class containing some useful methods used by command line tools
Constants	Some useful constants.
Counter	Simple counter class
DocIdSetBuilder	A builder of DocIdSets.
DocIdSetBuilder.BulkAdder	Utility class to efficiently add many docs in one go.
FilterIterator<T,InnerT extends T>	An Iterator implementation that filters elements with a boolean predicate.
FixedBitSet	BitSet of fixed length (numBits), backed by accessible (FixedBitSet.getBits()) long[], accessed with an int index, implementing Bits and DocIdSet.
FrequencyTrackingRingBuffer	A ring buffer that tracks the frequency of the integers that it contains.
FutureArrays	Additional methods from Java 9's java.util.Arrays.
FutureObjects	Additional methods from Java 9's java.util.Objects.
InfoStream	Debugging API for Lucene classes such as IndexWriter and SegmentInfos.
InPlaceMergeSorter	Sorter implementation based on the merge-sort algorithm that merges in place (no extra memory will be allocated).
IntBlockPool	A pool for int blocks similar to ByteBlockPool
IntBlockPool.Allocator	Abstract class for allocating and freeing int blocks.
IntBlockPool.DirectAllocator	A simple IntBlockPool.Allocator that never recycles.
IntBlockPool.SliceReader	A IntBlockPool.SliceReader that can read int slices written by a IntBlockPool.SliceWriter
IntBlockPool.SliceWriter	A IntBlockPool.SliceWriter that allows to write multiple integer slices into a given IntBlockPool.
IntroSelector	Implementation of the quick select algorithm.
IntroSorter	Sorter implementation based on a variant of the quicksort algorithm called introsort: when the recursion level exceeds the log of the length of the array to sort, it falls back to heapsort.
IntsRef	Represents int[], as a slice (offset + length) into an existing int[].
IntsRefBuilder	A builder for IntsRef instances.
IOUtils	This class emulates the new Java 7 "Try-With-Resources" statement.
LongBitSet	BitSet of fixed length (numBits), backed by accessible (LongBitSet.getBits()) long[], accessed with a long index.
LongsRef	Represents long[], as a slice (offset + length) into an existing long[].
LongValues	Abstraction over an array of longs.
LSBRadixSorter	A LSB Radix sorter for unsigned int values.
MapOfSets<K,V>	Helper class for keeping Lists of Objects associated with keys.
MathUtil	Math static utility methods.
MergedIterator<T extends Comparable<T>>	Provides a merged sorted view from several sorted iterators.
MSBRadixSorter	Radix sorter for variable-length strings.
NamedSPILoader<S extends NamedSPILoader.NamedSPI>	Helper class for loading named SPIs from classpath (e.g.
NamedThreadFactory	A default ThreadFactory implementation that accepts the name prefix of the created threads as a constructor argument.
NotDocIdSet	This DocIdSet encodes the negation of another DocIdSet.
NumericUtils	Helper APIs to encode numeric values as sortable bytes and vice-versa.
OfflineSorter	On-disk sorting of byte arrays.
OfflineSorter.BufferSize	A bit more descriptive unit for constructors.
OfflineSorter.ByteSequencesReader	Utility class to read length-prefixed byte[] entries from an input.
OfflineSorter.ByteSequencesWriter	Utility class to emit length-prefixed byte[] entries to an output stream for sorting.
PagedBytes	Represents a logical byte[] as a series of pages.
PagedBytes.Reader	Provides methods to read BytesRefs from a frozen PagedBytes.
PrintStreamInfoStream	InfoStream implementation over a PrintStream such as System.out.
PriorityQueue<T>	A PriorityQueue maintains a partial ordering of its elements such that the least element can always be found in constant time.
QueryBuilder	Creates queries from the Analyzer chain.
QueryBuilder.TermAndBoost	Wraps a term and boost
RadixSelector	Radix selector.
RamUsageEstimator	Estimates the size (memory representation) of Java objects.
RecyclingByteBlockAllocator	A ByteBlockPool.Allocator implementation that recycles unused byte blocks in a buffer and reuses them in subsequent calls to RecyclingByteBlockAllocator.getByteBlock().
RecyclingIntBlockAllocator	A IntBlockPool.Allocator implementation that recycles unused int blocks in a buffer and reuses them in subsequent calls to RecyclingIntBlockAllocator.getIntBlock().
RefCount<T>	Manages reference counting for a given object.
RoaringDocIdSet	DocIdSet implementation inspired from http://roaringbitmap.org/ The space is divided into blocks of 2^16 bits and each block is encoded independently.
RoaringDocIdSet.Builder	A builder of RoaringDocIdSets.
RollingBuffer<T extends RollingBuffer.Resettable>	Acts like forever growing T[], but internally uses a circular buffer to reuse instances of T.
SameThreadExecutorService	An ExecutorService that executes tasks immediately in the calling thread during submit.
Selector	An implementation of a selection algorithm, ie.
SentinelIntSet	A native int hash-based set where one value is reserved to mean "EMPTY" internally.
SetOnce<T>	A convenient class which offers a semi-immutable object wrapper implementation which allows one to set the value of an object exactly once, and retrieve it many times.
SloppyMath	Math functions that trade off accuracy for speed.
SmallFloat	Floating point numbers smaller than 32 bits.
Sorter	Base class for sorting algorithms implementations.
SparseFixedBitSet	A bit set that only stores longs that have at least one bit which is set.
SPIClassIterator<S>	Helper class for loading SPI classes from classpath (META-INF files).
StableMSBRadixSorter	Stable radix sorter for variable-length strings.
StringHelper	Methods for manipulating strings.
TimSorter	Sorter implementation based on the TimSort algorithm.
ToStringUtils	Helper methods to ease implementing Object.toString().
UnicodeUtil	Class to encode java's UTF16 char[] into UTF8 byte[] without always allocating a new byte[] as String.getBytes(StandardCharsets.UTF_8) does.
Version	Use by certain classes to match version compatibility across releases of Lucene.
VirtualMethod<C>	A utility for keeping backwards compatibility on previously abstract methods (or similar replacements).
WeakIdentityMap<K,V>	Implements a combination of WeakHashMap and IdentityHashMap.

Exception Summary

Exception	Description
BytesRefHash.MaxBytesLengthExceededException	Thrown if a BytesRef exceeds the BytesRefHash limit of ByteBlockPool.BYTE_BLOCK_SIZE-2.
SetOnce.AlreadySetException	Thrown when SetOnce.set(Object) is called more than once.
ThreadInterruptedException	Thrown by lucene on detecting that Thread.interrupt() had been called.

Annotation Types Summary

Annotation Type	Description
SuppressForbidden	Annotation to suppress forbidden-apis errors inside a whole class, a method, or a field.

Package org.apache.lucene.util Description

Some utility classes.