Please whitelist java.util.concurrent.atomic.AtomicInteger, currently this must be approved explicitly otherwise a

def cnt = new java.util.concurrent.atomic.AtomicInteger(42)

results in

org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use new java.util.concurrent.atomic.AtomicInteger int

Rationale for using this is ensuring there are no concurrency issues when using parallel pipeline stages. The curent implementation of the Jenkins pipeline may not have concurrency issues, but that could change in the future and parallel code should be written in a proper way no to make assumptions