Hi Rastin,
If you are using maven, check your $M2_HOME directory to make sure you have mongo-java-driver there. Alternatively, check your java classpath for the driver.
Can you please post:
mongo-java-driver that you are using. pom.xml for the mongo dependencies. See MongoDB Java Driver Quick Tour (v3.2) for examples and guides, which may be useful as well.
Regards,
Wan.