public void write(DataOutput out) throws IOException {
out.writeBoolean(isNode);
if (node != null) {
node.write(out);
} else {
contribution.write(out);
}
}
public void readFields(DataInput in) throws IOException {
isNode = in.readBoolean();
if (isNode) {
node = new PageRankNode();
node.readFields(in);
} else {
contribution = new Contribution();
contribution.readFields(in);
}
}