JDK 7类文件向后兼容JDK 6

Which features of JDK 7 (excluding invokedynamic because it is not used by java) causing a new class file version which is not compliant with JDK 6. It seams that all features could be implemented by compiler generating glue codes. For example String in switch statement could be implemented using repeated ifeq statements generated by the compiler. I want to able to give -source 1.7 -target 1.6 flags to compiler to be compliant with jre 6 and at the same time use project coin features in jdk 7.Which features of JDK 7 (excluding invokedynami