If you work with JDeveloper 12.1.3 you may missing the return type of methods in completion insight.
For an example you hit CTRL-SPACE after following code
you see that at the start and at the end of the popup the available method names and parameter. If you have worked before with older versions of JDeveloper, you know that there is shown the return type of the method at the end. What a loose of productivity!
You run into Bug 19353293 : CODE INSIGHT : RETURN TYPE NOT SHOWN.
But no problem, there exist patch 19353293: CODE INSIGHT : RETURN TYPE NOT SHOWN, which solves the problem for you:
Remember to install the patches for all of your developers!
Remember too, if you want to install more than one patch, there can be conflicts. Please test carefully, if all of your problems are solved for all patches after adding one more patch. Maybe you have to create a merge request in Oracle My Support.