public interface WritableComparable<T> extends Writable, java.lang.Comparable<T>
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.
Example:
public class MyWritableComparable implements WritableComparable {
// Some data
private int counter;
private long timestamp;
public void write(DataOutput out) throws IOException {
out.writeInt(counter);
out.writeLong(timestamp);
}
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));
}
}