今天用android studio 3.0新建了一个kotlin的工程，用gradlew编译代码，出现错误：
FAILURE: Build failed with an exception.
Where:
Build file ‘xxx/build.gradle’ line: 1What went wrong:
xxxjava.lang.UnsupportedClassVersionError: com/android/build/gradle/AppPlugin : Unsupported major.minor version 52.0
Try:
Run with –stacktrace option to get the stack trace. Run with –info or –debug option to get more log output.
BUILD FAILED
原因是Kotlin需要jdk 1.8的支持，就是说java的编译环境版本太低，java 8 class file的版本是52，Java 7虚拟机只能支持到51。所以需要升级到java 8 vm才行。