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## 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.

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