It is not allowed on DBCursor.addOption, but it is on DBCursor.setOption. Here's what happens if you use it:

import com.mongodb.*
import java.net.UnknownHostException;

public class ExhaustTest {
public static void main(String[] args) throws UnknownHostException {
MongoClient client = new MongoClient();
DBCollection coll = client.getDB("test").getCollection("CS6843");
for (int i = 0; i < 100000; i++)

DBCursor cursor = coll.find();
cursor.setOptions(Bytes.QUERYOPTION_EXHAUST);
cursor.toArray(10000);
}
}

Exception in thread "main" com.mongodb.MongoException: ids don't match
	at com.mongodb.DBTCPConnector.innerCall(DBTCPConnector.java:246)
	at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:216)
	at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:184)
	at com.mongodb.DBApiLayer$Result._advance(DBApiLayer.java:430)
	at com.mongodb.DBApiLayer$Result.hasNext(DBApiLayer.java:399)
	at com.mongodb.DBCursor._hasNext(DBCursor.java:464)
	at com.mongodb.DBCursor._fill(DBCursor.java:518)
	at com.mongodb.DBCursor.toArray(DBCursor.java:553)