Interface WritableComparable<T>

All Superinterfaces:
Comparable<T>, Writable
All Known Implementing Classes:
BooleanWritable, BytesWritable, ByteWritable, DocumentID, DoubleWritable, FloatWritable, ID, ID, IntWritable, JobID, JobID, Key, LongWritable, MD5Hash, MultiFileWordCount.WordOffset, NullWritable, Record, RecordTypeInfo, SecondarySort.IntPair, Shard, TaskAttemptID, TaskAttemptID, TaskID, TaskID, Text, TypedBytesWritable, UTF8, VIntWritable, VLongWritable

public interface WritableComparable<T>
extends Writable, Comparable<T>

A Writable which is also Comparable.

WritableComparables can be compared to each other, typically via Comparators. Any type which is to be used as a key in the Hadoop Map-Reduce framework should implement this interface.


     public class MyWritableComparable implements WritableComparable {
       // Some data
       private int counter;
       private long timestamp;
       public void write(DataOutput out) throws IOException {
       public void readFields(DataInput in) throws IOException {
         counter = in.readInt();
         timestamp = in.readLong();
       public int compareTo(MyWritableComparable w) {
         int thisValue = this.value;
         int thatValue = ((IntWritable)o).value;
         return (thisValue < thatValue ? -1 : (thisValue==thatValue ? 0 : 1));

Method Summary
Methods inherited from interface
readFields, write
Methods inherited from interface java.lang.Comparable

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