Package org.apache.lucene.util

Some utility classes.

Interface Summary

Interface	Description
Attribute	Base interface for attributes.
AttributeReflector	This interface is used to reflect contents of AttributeSource or AttributeImpl.
Bits	Interface for Bitset-like structures.
BytesRefIterator	A simple iterator interface for BytesRef iteration.
MutableBits	Extension of Bits for live documents.
NamedSPILoader.NamedSPI	Interface to support NamedSPILoader.lookup(String) by name.
RollingBuffer.Resettable	Implement to reset an instance

Class Summary

Class	Description
ArrayUtil	Methods for manipulating arrays.
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.AttributeFactory	An AttributeFactory creates instances of AttributeImpls.
AttributeSource.State	This class holds the state of an AttributeSource.
Bits.MatchAllBits	Bits impl of the specified length with all bits set.
Bits.MatchNoBits	Bits impl of the specified length with no bits set.
BitUtil	A variety of high efficiency bit twiddling routines.
BroadWord	Methods and constants inspired by the article "Broadword Implementation of Rank/Select Queries" by Sebastiano Vigna, January 30, 2012: algorithm 1: BroadWord.bitCount(long), count of set bits in a long algorithm 2: BroadWord.select(long, int), selection of a set bit in a long, bytewise signed smaller <8 operator: BroadWord.smallerUpTo7_8(long,long).
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[].
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[].
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
DocIdBitSet	Simple DocIdSet and DocIdSetIterator backed by a BitSet
DoubleBarrelLRUCache<K extends DoubleBarrelLRUCache.CloneableKey,V>	Simple concurrent LRU cache, using a "double barrel" approach where two ConcurrentHashMaps record entries.
DoubleBarrelLRUCache.CloneableKey	Object providing clone(); the key class must subclass this.
FieldCacheSanityChecker	Provides methods for sanity checking that entries in the FieldCache are not wasteful or inconsistent.
FieldCacheSanityChecker.Insanity	Simple container for a collection of related CacheEntry objects that in conjunction with each other represent some "insane" usage of the FieldCache.
FieldCacheSanityChecker.InsanityType	An Enumeration of the different types of "insane" behavior that may be detected in a FieldCache.
FilterIterator<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.
FixedBitSet.FixedBitSetIterator	A DocIdSetIterator which iterates over set bits in a FixedBitSet.
GrowableByteArrayDataOutput	A DataOutput that can be used to build a byte[].
IndexableBinaryStringTools	Deprecated. Implement TermToBytesRefAttribute and store bytes directly instead.
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.
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[].
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.
MapOfSets<K,V>	Helper class for keeping Lists of Objects associated with keys.
MathUtil	Math static utility methods.
MergedIterator<T extends java.lang.Comparable<T>>	Provides a merged sorted view from several sorted iterators.
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.
NumericUtils	This is a helper class to generate prefix-encoded representations for numerical values and supplies converters to represent float/double values as sortable integers/longs.
NumericUtils.IntRangeBuilder	Callback for NumericUtils.splitIntRange(org.apache.lucene.util.NumericUtils.IntRangeBuilder, int, int, int).
NumericUtils.LongRangeBuilder	Callback for NumericUtils.splitLongRange(org.apache.lucene.util.NumericUtils.LongRangeBuilder, int, long, long).
OpenBitSet	An "open" BitSet implementation that allows direct access to the array of words storing the bits.
OpenBitSetDISI	OpenBitSet with added methods to bulk-update the bits from a DocIdSetIterator.
OpenBitSetIterator	An iterator to iterate over set bits in an OpenBitSet.
PagedBytes	Represents a logical byte[] as a series of pages.
PagedBytes.Reader	Provides methods to read BytesRefs from a frozen PagedBytes.
PForDeltaDocIdSet	DocIdSet implementation based on pfor-delta encoding.
PForDeltaDocIdSet.Builder	A builder for PForDeltaDocIdSet.
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.
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.
RollingBuffer<T extends RollingBuffer.Resettable>	Acts like forever growing T[], but internally uses a circular buffer to reuse instances of T.
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.
SPIClassIterator<S>	Helper class for loading SPI classes from classpath (META-INF files).
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("UTF-8") does.
VirtualMethod<C>	A utility for keeping backwards compatibility on previously abstract methods (or similar replacements).
WAH8DocIdSet	DocIdSet implementation based on word-aligned hybrid encoding on words of 8 bits.
WAH8DocIdSet.Builder	A builder for WAH8DocIdSets.
WeakIdentityMap<K,V>	Implements a combination of WeakHashMap and IdentityHashMap.

Enum Summary

Enum	Description
RamUsageEstimator.JvmFeature	JVM diagnostic features.
Version	Use by certain classes to match version compatibility across releases of Lucene.

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.