Why I always meet this error?

I want to write a opentool, but when I compile the files, it will occur this error:

Error: line (3) cannot access com.intellij.openapi.actionSystem.AnAction
bad class file: D:\IntelliJ-IDEA-3.0.2\lib\openapi.jar(com/intellij/openapi/actionSystem/AnAction.class)
class file has wrong version 48.0, should be 47.0
Please remove or make sure it appears in the correct subdirectory of the classpath.