tl.lin.data.map

Class HashMapWritable<K extends org.apache.hadoop.io.Writable,V extends org.apache.hadoop.io.Writable>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

tl.lin.data.map.HashMapWritable<K,V>

Type Parameters:

K - type of the key

V - type of the value

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>, org.apache.hadoop.io.Writable

public class HashMapWritable<K extends org.apache.hadoop.io.Writable,V extends org.apache.hadoop.io.Writable>
extends HashMap<K,V>
implements org.apache.hadoop.io.Writable

Writable extension of a Java HashMap. This generic class supports the use of any type as either key or value. For a feature vector, HMapKIW, HMapKFW, and a family of related classes provides a more efficient implementation.

There are a number of key differences between this class and Hadoop's MapWritable:

• MapWritable is more flexible in that it supports heterogeneous elements. In this class, all keys must be of the same type and all values must be of the same type. This assumption allows a simpler serialization protocol and thus is more efficient. Run main in this class for a simple efficiency test.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Constructor Summary

Constructors

Constructor and Description
HashMapWritable() Creates a HashMapWritable object.
HashMapWritable(HashMap<K,V> map) Creates a HashMapWritable object from a regular HashMap.

Method Summary

Methods

Modifier and Type	Method and Description
void	readFields(DataInput in) Deserializes the array.
void	write(DataOutput out) Serializes this array.

Methods inherited from class java.util.HashMap

clear, clone, containsKey, containsValue, entrySet, get, isEmpty, keySet, put, putAll, remove, size, values

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

HashMapWritable

public HashMapWritable()

Creates a HashMapWritable object.

HashMapWritable

public HashMapWritable(HashMap<K,V> map)

Creates a HashMapWritable object from a regular HashMap.

Method Detail

readFields

public void readFields(DataInput in)
                throws IOException

Deserializes the array.

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Parameters:

in - source for raw byte representation

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

Serializes this array.

Specified by:

write in interface org.apache.hadoop.io.Writable

Parameters:

out - where to write the raw byte representation

Throws:

IOException