Eclipse does not highlight matching variables

Question

Try:

window > preferences > java > editor > mark occurrences 

Select all options available there.

Also go to:

Preferences > General > Editors > Text Editors > Annotations

Compare the settings for 'Occurrences' and 'Write Occurrences'

Make sure that you don't have the 'Text as higlighted' option checked for one of them.

This should fix it.

Alt + Shift + o
Will solve your problem and agree with @Korhan Ozturk as well :)

This is known as Toggle Mark occurrence (Alt + Shift + O), Means will highlight all occurrence of focused variable. Same thing can be achieved from tool bar as follows

In same tool bar there is another switch if you turn that on you will see complete path for opened file, That is Breadcrumb

there are some more very useful switches like word wrap, Show white Characters just after toggle mark occurrence

There is a bug in Eclipse Juno (and probably others) but I have a workaround!

If you have already checked all the configurations mentioned in the top answers here and it's STILL not working try this.

To confirm the problem:

1. Select a variable
2. Notice the highlight didn't work
3. Click away from eclipse so the editor loses focus.
4. Click on eclipse's title bar so it regains focus, your variable should be highlighted.

If this is happening for you, you must close ALL of your open files and reopen them. This bug seems to also make weird things happen with Ctrl+S saving of an individual file. My guess is that something is happening whereby internally eclipse believes a certain file has focus but it actually doesn't, and the UI's state is rendered as though a different file is being edited.

Edit: If it's STILL not working, you might need to restart eclipse, but if you don't want to, try selecting the item you want to see occurrences of then disable and re-enable the Mark Occurences Toggle button.

The only that worked for me was:

Java > Editor > Mark Occurrences:
Check "Mark occurrences of te selected element in the current file."
... and maybe all the ones below.