In pre-modular world, some tools (e.g. JMH -prof gc) used ThreadMXBean to gain access to interesting methods like getThreadAllocatedBytes. In post-modular world, trying to do the usual trick fails either on setAccessible on non-exported method, or later during the invocation.

            ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
            try {
                getBytes = threadMXBean.getClass().getMethod("getThreadAllocatedBytes", long[].class);
                getBytes.setAccessible(true);
            } catch (Throwable e) {
                ...
            }

While -XaddExports:jdk.management/com.sun.management.internal=ALL-UNNAMED works as workaround, it seems better to just move the contents of ThreadMXBean from internal to public interface.