driver-legacy/src/main/com/mongodb/DBCollection.java
public DBCollection rename(final String newName, final boolean dropTarget) {
        try {
            executor.execute(new RenameCollectionOperation(getNamespace(),
                                                           new MongoNamespace(getNamespace().getDatabaseName(), newName), getWriteConcern())
                                     .dropTarget(dropTarget), getReadConcern());
            return getDB().getCollection(newName);
        } catch (MongoWriteConcernException e) {
            throw createWriteConcernException(e);
        }
    }
public DBCollection rename(final String newName, final boolean dropTarget) {
        try {
            executor.execute(new RenameCollectionOperation(getNamespace(),
                                                           new MongoNamespace(getNamespace().getDatabaseName(), newName), getWriteConcern())
                                     .dropTarget(dropTarget), getReadConcern());
            return getDB().getCollection(newName);
        } catch (MongoWriteConcernException e) {
            throw createWriteConcernException(e);
        }
    }
Change the name of an existing collection.

@param newName    specifies the new name of the collection
@param dropTarget If {@code true}, mongod will drop the collection with the target name if it exists
@return the collection with new name
@throws MongoException if target is the name of an existing collection and {@code dropTarget=false}.
@mongodb.driver.manual reference/command/renameCollection/ Rename Collection