[java] Eclipse does not highlight matching variables

For others running into this without any of the above solutions working AND you have modified the default theme, you might want to check the highlight color for occurrences.

Preferences > General > Editors > Text Editors > Annotations

Then select Occurrences in the Annotation Types, and change the Color Box to something other than your background color in your editor. You can also change the Highlight to a outline box by Checking "Text as" and selecting "Box" from the drop-down box (which is easier to see various syntax colors then with the highlights)