p2pMapReduce.mapreduceModule.io
Interface WritableComparable<T>
- All Superinterfaces:
- java.lang.Comparable<T>, Writable
- All Known Implementing Classes:
- IntWritable, LongWritable, NullWritable, StringWritable
public interface WritableComparable<T>
- extends Writable, java.lang.Comparable<T>
A Writable
which is also Comparable
.
WritableComparable
s can be compared to each other, typically
via Comparator
s. 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<MyWritableComparable> {
// 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 other) {
int thisValue = this.counter;
int thatValue = other.counter;
return (thisValue < thatValue ? -1 : (thisValue == thatValue ? 0 : 1));
}
}
Methods inherited from interface java.lang.Comparable |
compareTo |