The default `java.policy` no longer grants `stopThread` runtime permission in JDK 9.

In previous releases, untrusted code had the `stopThread` runtime permission by default. This allows untrusted code to call `Thread::stop` ( on threads other than the current one ). Having an arbitrary exception thrown asynchronously is not something that trusted code should be expected to handle gracefully. So this permission is removed by default in JDK 9. The following line is deleted from the file `conf/security/java.policy` : `permission java.lang.RuntimePermission "stopThread";`