org.apache.hadoop.io
Interfaces 
Closeable
RawComparator
SequenceFile.Sorter.RawKeyValueIterator
SequenceFile.ValueBytes
Stringifier
Writable
WritableComparable
WritableFactory
Classes 
AbstractMapWritable
ArrayFile
ArrayFile.Reader
ArrayFile.Writer
ArrayWritable
BinaryComparable
BloomMapFile
BloomMapFile.Reader
BloomMapFile.Writer
BooleanWritable
BooleanWritable.Comparator
BytesWritable
BytesWritable.Comparator
ByteWritable
ByteWritable.Comparator
CompressedWritable
DataInputBuffer
DataOutputBuffer
DefaultStringifier
DoubleWritable
DoubleWritable.Comparator
FloatWritable
FloatWritable.Comparator
GenericWritable
InputBuffer
IntWritable
IntWritable.Comparator
IOUtils
IOUtils.NullOutputStream
LongWritable
LongWritable.Comparator
LongWritable.DecreasingComparator
MapFile
MapFile.Reader
MapFile.Writer
MapWritable
MD5Hash
MD5Hash.Comparator
NullWritable
NullWritable.Comparator
ObjectWritable
OutputBuffer
SecureIOUtils
SequenceFile
SequenceFile.Metadata
SequenceFile.Reader
SequenceFile.Sorter
SequenceFile.Writer
SetFile
SetFile.Reader
SetFile.Writer
SortedMapWritable
Text
Text.Comparator
TwoDArrayWritable
UTF8
UTF8.Comparator
VersionedWritable
VIntWritable
VLongWritable
WritableComparator
WritableFactories
WritableName
WritableUtils
Enums 
SequenceFile.CompressionType
Exceptions 
MultipleIOException
SecureIOUtils.AlreadyExistsException
VersionMismatchException