I'm trying to run some Java 8 lambda expressions in a function in Pega 8.6, Personal Edition for a PoC, but am getting the following error message:

Method references are allowed only at source level 1.8 or above

The code I am running trying is:

  Files.walk(Paths.get(destDirPath))                 .filter(Files::isRegularFile)                 .map(Path::toFile)                 .forEach(File::delete);

Do I need to change any configuration to be able to run this?