It is not possible to parse Java libraries compiled with Java 8. This is problematic because Java 7 is not updated anymore. An upgrade to Java 8 is required.
The cause of the problem is the insufficient Java 8 support of the Apache BCEL library version that you use. The issue BCEL173 has already been solved for BCEL 6.0. Unfortunately, BCEL 6.0 is neither released nor announced to be released yet.
You might try the bcel-findbugs library instead, which has been suggest in the issue mentioned above for the time until BCEL 6.0 is released.