In Eclipse/MyEclipse, there is a wizard named ‘Find Broken Externalized Strings’ which can be used to search for unused keys in the properties files. It also highlights the unused keys as shown in the attached screenshot. To invoke the wizard, right click on the messages.properties file or on the corresponding package, select Source > Find Broken Externalized Strings, it will then list the unused keys in the Search view and automatically highlight them in the editor as well.
The only limitation to this feature is it will find the broken strings in the files that are generated using the ‘Externalize Strings’ wizard.
Right click on the java class > Source > Externalize Strings. This will generate the properties file with the strings from the code.
Attached is the screenshot for your reference.
Hope this helps. Please let us know if you have any further questions.