Eclipse: Enable autocomplete / content assist

By default in Eclipse you only have to press Ctrl + space for autocomplete. Then select the desired method and wait 500ms for the javadoc info to pop up. If this doesn't work go to the Eclipse Windows menu → Preferences → Java → Editor → Content assist and check your settings here

If you would like to use autocomplete all the time without having to worry about hitting Ctrl + Spacebar or your own keyboard shortcut, you can make the following adjustment in the Eclipse preferences to trigger autocomplete simply by typing several different characters:

1. Eclipse > Preferences > Java > Editor > Content Assist
2. Auto Activation > Auto activation triggers for Java
3. Enter all the characters you want to trigger autocomplete, such as the following:

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ._

Now any time that you type any of these characters, Eclipse will trigger autocomplete suggestions based on the context.

1. window->preferences->java->Editor->Contest Assist
   
2. Enter in Auto activation triggers for java:
   abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ._
   
3. Apply and Close
   

other method:
type initial letter then ctrl+spacebar for auto-complete options.