driver-embedded/src/main/com/mongodb/embedded/client/MongoClients.java
public static synchronized void close() {
        if (mongoEmbeddedLibrary != null) {
            try {
                mongoEmbeddedLibrary.close();
            } catch (Exception e) {
                throw new MongoClientEmbeddedException(format("Could not close the mongo embedded library.%n"
                        + "Please ensure that any MongoClient instances have been closed first.%n"
                        + "Server error message: %s", e.getMessage()), e);
            }
            mongoEmbeddedLibrary = null;

        }
    }
public static synchronized void close() {
        if (mongoEmbeddedLibrary != null) {
            try {
                mongoEmbeddedLibrary.close();
            } catch (Exception e) {
                throw new MongoClientEmbeddedException(format("Could not close the mongo embedded library.%n"
                        + "Please ensure that any MongoClient instances have been closed first.%n"
                        + "Server error message: %s", e.getMessage()), e);
            }
            mongoEmbeddedLibrary = null;

        }
    }
Closes down the mongod library