Package org.apache.lucene.util

Some utility classes.


Interface Summary
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
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.rank9(long), count of set bits in a long algorithm 2: BroadWord.select9(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 AtomicLong 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.
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.
LongsRef Represents long[], as a slice (offset + length) into an existing long[].
MapOfSets<K,V> Helper class for keeping Lists of Objects associated with keys.
MathUtil Math static utility methods.
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.
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().
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.
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
RamUsageEstimator.JvmFeature JVM diagnostic features.
Version Use by certain classes to match version compatibility across releases of Lucene.

Exception Summary
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.

Package org.apache.lucene.util Description

Some utility classes.

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