## Package org.apache.hadoop.io

Generic i/o code for use when reading and writing data to the network, to databases, and to files.

See:
Description

Interface Summary
Closeable: Deprecated. use java.io.Closeable
RawComparator<T>: A `Comparator` that operates directly on byte representations of objects.
SequenceFile.Sorter.RawKeyValueIterator: The interface to iterate over raw keys/values of SequenceFiles.
SequenceFile.ValueBytes: The interface to 'raw' values of SequenceFiles.
Stringifier<T>: Stringifier interface offers two methods to convert an object to a string representation and restore the object given its string representation.
Writable: A serializable object which implements a simple, efficient, serialization protocol, based on `DataInput` and `DataOutput`.
WritableComparable<T>: A `Writable` which is also `Comparable`.
WritableFactory: A factory for a class of Writable.

Class Summary
AbstractMapWritable: Abstract base class for MapWritable and SortedMapWritable Unlike org.apache.nutch.crawl.MapWritable, this class allows creation of MapWritable<Writable, MapWritable> so the CLASS_TO_ID and ID_TO_CLASS maps travel with the class instead of being static.
ArrayFile: A dense file-based mapping from integers to values.
ArrayFile.Reader: Provide access to an existing array file.
ArrayFile.Writer: Write a new array file.
ArrayWritable: A Writable for arrays containing instances of a class.
BinaryComparable: Interface supported by `WritableComparable` types supporting ordering/permutation by a representative set of bytes.
BloomMapFile: This class extends `MapFile` and provides very much the same functionality.
BloomMapFile.Reader
BloomMapFile.Writer
BooleanWritable: A WritableComparable for booleans.
BooleanWritable.Comparator: A Comparator optimized for BooleanWritable.
BytesWritable: A byte sequence that is usable as a key or value.
BytesWritable.Comparator: A Comparator optimized for BytesWritable.
ByteWritable: A WritableComparable for a single byte.
ByteWritable.Comparator: A Comparator optimized for ByteWritable.
CompressedWritable: A base-class for Writables which store themselves compressed and lazily inflate on field access.
DataInputBuffer: A reusable `DataInput` implementation that reads from an in-memory buffer.
DataOutputBuffer: A reusable `DataOutput` implementation that writes to an in-memory buffer.
DefaultStringifier<T>: DefaultStringifier is the default implementation of the `Stringifier` interface which stringifies the objects using base64 encoding of the serialized version of the objects.
DoubleWritable: Writable for Double values.
DoubleWritable.Comparator: A Comparator optimized for DoubleWritable.
FloatWritable: A WritableComparable for floats.
FloatWritable.Comparator: A Comparator optimized for FloatWritable.
GenericWritable: A wrapper for Writable instances.
InputBuffer: A reusable `InputStream` implementation that reads from an in-memory buffer.
IntWritable: A WritableComparable for ints.
IntWritable.Comparator: A Comparator optimized for IntWritable.
IOUtils: An utility class for I/O related functionality.
IOUtils.NullOutputStream: /dev/null of OutputStreams.
LongWritable: A WritableComparable for longs.
LongWritable.Comparator: A Comparator optimized for LongWritable.
LongWritable.DecreasingComparator: A decreasing Comparator optimized for LongWritable.
MapFile: A file-based map from keys to values.
MapFile.Reader: Provide access to an existing map.
MapFile.Writer: Writes a new map.
MapWritable: A Writable Map.
MD5Hash: A Writable for MD5 hash values.
MD5Hash.Comparator: A WritableComparator optimized for MD5Hash keys.
NullWritable: Singleton Writable with no data.
NullWritable.Comparator: A Comparator "optimized" for NullWritable.
ObjectWritable: A polymorphic Writable that writes an instance with it's class name.
OutputBuffer: A reusable `OutputStream` implementation that writes to an in-memory buffer.
SecureIOUtils: This class provides secure APIs for opening and creating files on the local disk.
SequenceFile: `SequenceFile`s are flat files consisting of binary key/value pairs.
SequenceFile.Metadata: The class encapsulating with the metadata of a file.
SequenceFile.Reader: Reads key/value pairs from a sequence-format file.
SequenceFile.Sorter: Sorts key/value pairs in a sequence-format file.
SequenceFile.Writer: Write key/value pairs to a sequence-format file.
SetFile: A file-based set of keys.
SetFile.Reader: Provide access to an existing set file.
SetFile.Writer: Write a new set file.
SortedMapWritable: A Writable SortedMap.
Text: This class stores text using standard UTF8 encoding.
Text.Comparator: A WritableComparator optimized for Text keys.
TwoDArrayWritable: A Writable for 2D arrays containing a matrix of instances of a class.
UTF8: Deprecated. replaced by Text
UTF8.Comparator: A WritableComparator optimized for UTF8 keys.
VersionedWritable: A base class for Writables that provides version checking.
VIntWritable: A WritableComparable for integer values stored in variable-length format.
VLongWritable: A WritableComparable for longs in a variable-length format.
WritableComparator: A Comparator for `WritableComparable`s.
WritableFactories: Factories for non-public writables.
WritableName: Utility to permit renaming of Writable implementation classes without invalidiating files that contain their class name.
WritableUtils

Enum Summary
SequenceFile.CompressionType: The compression type used to compress key/value pairs in the `SequenceFile`.

Exception Summary
MultipleIOException: Encapsulate a list of `IOException` into an `IOException`
SecureIOUtils.AlreadyExistsException: Signals that an attempt to create a file at a given pathname has failed because another file already existed at that path.
VersionMismatchException: Thrown by `VersionedWritable.readFields(DataInput)` when the version of an object being read does not match the current implementation version as returned by `VersionedWritable.getVersion()`.

## Package org.apache.hadoop.io Description

Generic i/o code for use when reading and writing data to the network, to databases, and to files.

Copyright © 2009 The Apache Software Foundation