Cannot switch on a value of type String for source level below 1.7. only convertible int values or enum variables is permitted

When writing the switch code in Java, the parameters are in string, JDK use is 1.8, but still error, said does not support the 1.7 version of the following, and then find some files in the project, open a file as follows, found to be 1.6 version, it is very strange ah, according to the eclipse hint, the version of 1.7, you can.

Cannot switch on a value of type String for source level below 1.7. only convertible int values or enum variables is permitted