Eclipse dot(.) Content Assist is not working ?

Some day I try to upgrade my Eclipse, and let me stuck on android app write.
And then restore the backup configuration.

The Eclipse Content assist isn't working!

A couple of hours work, the crazy problem is solved.

Configure Eclipse’s content assist, go “Preferences>Java>Editor>Content Assist>Advanced“. Make sure “Other Java Proposals” is ticked

Reference article is from Here