Lost the ability to fold code in eclipse
Method 1:
Window -> Preferences -> Java -> Editor ->Folding
Method 2
ctrl + NUMPAD-/
Method 3
Right-click where line-numbers are (should be). Go to Folding -> Enable Folding.
Folding is configured under Window -> Preferences -> Java -> Editor ->Folding
The Preferences window has a search box - very useful to find even the most obscure options.