Restoring the default options will help you.
Use these steps to restore the default options:
Windows --> Preferences --> Java --> Editor --> Content Assist --> Advanced
Here's an example of the sort of data you see in this preference screen, however not certain what you currently have.
NOTE: In case duplicate Mylyn entries, uncheck the duplicate entries that do not contain "(Mylyn)" in their name
Also, see this, it defines the default list to restore:
Select the proposal kinds contained in the 'default' content assist list:
Other Java Proposals,
SWT Template Proposals,