driver-legacy/src/main/com/mongodb/DBCollection.java
public WriteResult update(final DBObject query, final DBObject update) {
        return update(query, update, false, false);
    }
public WriteResult update(final DBObject query, final DBObject update) {
        return update(query, update, false, false);
    }
Modify an existing document. The query parameter employs the same query selectors, as used in {@code find()}.

@param query  the selection criteria for the update
@param update the modifications to apply
@return the result of the operation
@throws com.mongodb.DuplicateKeyException if the write failed to a duplicate unique key
@throws com.mongodb.WriteConcernException if the write failed due some other failure specific to the update command
@throws MongoException if the operation failed for some other reason
@mongodb.driver.manual tutorial/modify-documents/ Modify Documents