When I build the android project, it show \"Duplicate class\" exception,
1 exception was raised by workers: java.lang.RuntimeException:
java.lang.RuntimeEx
You can use search everywhere dialog(Dialog that opens on pressing shift twice).
Simply copy class name and paste it in search dialog and it will show results in drop down. You can browse result and check for duplicate entries, Complete path of class will be displayed next to class name so you can find relative libraries and can safely exclude it from anyone of the library.