K
- type of the keyV
- type of the valuepublic 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.AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>
Constructor and Description |
---|
HashMapWritable()
Creates a HashMapWritable object.
|
HashMapWritable(HashMap<K,V> map)
Creates a HashMapWritable object from a regular HashMap.
|
Modifier and Type | Method and Description |
---|---|
void |
readFields(DataInput in)
Deserializes the array.
|
void |
write(DataOutput out)
Serializes this array.
|
clear, clone, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, forEach, get, getOrDefault, isEmpty, keySet, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values
equals, hashCode, toString
public void readFields(DataInput in) throws IOException
readFields
in interface org.apache.hadoop.io.Writable
in
- source for raw byte representationIOException
public void write(DataOutput out) throws IOException
write
in interface org.apache.hadoop.io.Writable
out
- where to write the raw byte representationIOException
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