driver-legacy/src/main/com/mongodb/DBCollection.java
public WriteResult update(final DBObject query, final DBObject update, final boolean upsert, final boolean multi,
                              final WriteConcern concern, @Nullable final DBEncoder encoder) {
        return update(query, update, upsert, multi, concern, null, encoder);
    }
public WriteResult update(final DBObject query, final DBObject update, final boolean upsert, final boolean multi,
                              final WriteConcern concern, @Nullable final DBEncoder encoder) {
        return update(query, update, upsert, multi, concern, null, encoder);
    }
Modify an existing document or documents in collection. By default the method updates a single 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
@param upsert        when true, inserts a document if no document matches the update query criteria
@param multi         when true, updates all documents in the collection that match the update query criteria, otherwise only updates
one
@param concern       {@code WriteConcern} to be used during operation
@param encoder       {@code DBEncoder} to be used
@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