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java.lang.Objectorg.apache.nutch.io.MapFile.Reader
Provide access to an existing map.
Constructor Summary | |
MapFile.Reader(NutchFileSystem nfs,
String dirName)
Construct a map reader for the named map. |
|
MapFile.Reader(NutchFileSystem nfs,
String dirName,
WritableComparator comparator)
Construct a map reader for the named map using the named comparator. |
Method Summary | |
void |
close()
Close the map. |
void |
finalKey(WritableComparable key)
Reads the final key from the file. |
Writable |
get(WritableComparable key,
Writable val)
Return the value for the named key, or null if none exists. |
Class |
getKeyClass()
Returns the class of keys in this file. |
Class |
getValueClass()
Returns the class of values in this file. |
boolean |
next(WritableComparable key,
Writable val)
Read the next key/value pair in the map into key and
val . |
void |
reset()
Re-positions the reader before its first key. |
boolean |
seek(WritableComparable key)
Positions the reader at the named key, or if none such exists, at the first entry after the named key. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public MapFile.Reader(NutchFileSystem nfs, String dirName) throws IOException
public MapFile.Reader(NutchFileSystem nfs, String dirName, WritableComparator comparator) throws IOException
Method Detail |
public Class getKeyClass()
public Class getValueClass()
public void reset() throws IOException
IOException
public void finalKey(WritableComparable key) throws IOException
key
- key to read into
IOException
public boolean seek(WritableComparable key) throws IOException
IOException
public boolean next(WritableComparable key, Writable val) throws IOException
key
and
val
. Returns true if such a pair exists and false when at
the end of the map
IOException
public Writable get(WritableComparable key, Writable val) throws IOException
IOException
public void close() throws IOException
IOException
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