Error: Cannot switch on a value of type String. Only convertible int values or enum constants are permitted EVEN WITH JDK 1.7.

I have to build a project which has a code that uses the 'String in switch case' feature. Even though the compiler is set to jdk 1.7, the build fails showing that error. I checked the compiler settings in my sandbox, and set jdk 1.7 everywhere. The error is not shown in my sandbox, but then when I build, compilation error pops up saying "Cannot switch on a value of type String. Only convertible int values or enum constants are permitted". Even in build tool, the compiler is set to jdk 1.7