# 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
  Interface | Description
  --- | ---
  ByteBufferPool |
  Closeable | Deprecated use java.io.Closeable
  RawComparator<T> | A `Comparator` that operates directly on byte representations of objects.
  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
  Class | Description
  --- | ---
  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.
  ArrayPrimitiveWritable | This is a wrapper class.
  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.
  BooleanWritable | A WritableComparable for booleans.
  BytesWritable | A byte sequence that is usable as a key or value.
  ByteWritable | A WritableComparable for a single byte.
  CompressedWritable | A base-class for Writables which store themselves compressed and lazily inflate on field access.
  DataOutputOutputStream | OutputStream implementation that wraps a DataOutput.
  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.
  ElasticByteBufferPool | This is a simple ByteBufferPool which just creates ByteBuffers as needed.
  EnumSetWritable<E extends Enum<E>> | A Writable wrapper for EnumSet.
  FloatWritable | A WritableComparable for floats.
  GenericWritable | A wrapper for Writable instances.
  IntWritable | A WritableComparable for ints.
  IOUtils | An utility class for I/O related functionality.
  LongWritable | A WritableComparable for longs.
  MapFile | A file-based map from keys to values.
  MapWritable | A Writable Map.
  MD5Hash | A Writable for MD5 hash values.
  NullWritable | Singleton Writable with no data.
  ObjectWritable | A polymorphic Writable that writes an instance with it's class name.
  SequenceFile | `SequenceFile`s are flat files consisting of binary key/value pairs.
  SetFile | A file-based set of keys.
  ShortWritable | A WritableComparable for shorts.
  SortedMapWritable<K extends WritableComparable<? super K>> | A Writable SortedMap.
  Text | This class stores text using standard UTF8 encoding.
  TwoDArrayWritable | A Writable for 2D arrays containing a matrix of instances of a class.
  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.
  WritableUtils |

- Exception Summary
  Exception | Description
  --- | ---
  MultipleIOException | Encapsulate a list of `IOException` into an `IOException`
  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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