All those who are facing problem like "server error", "http error" or "java operation error".
Follow the steps provided below.
Step 1. Make sure you are using the latest version of WhatsApp.
Step 2. The access point whichever you are using should be default for all apps.
for this go to Settings > Configurations > Preferred Access Point.
Step 3. Restart your phone.
and
If you are still facing the problem get fresh internet settings from your operator.