public long[] getThreadIds() {
    return delegate.get().getThreadIds();
  }
Returns an array of {@code Thread Ids} that are directly in the {@code ExecutorService}'s
{@code ThreadGroup} excluding subgroups. {@code long[]} is returned to facilitate using JDK
APIs such as {@code ThreadMXBean#getThreadInfo(long[], int)}.

@return an array of {@code Thread Ids} that are directly in the {@code ExecutorService}'s
        {@code ThreadGroup} excluding subgroups
geode-dunit/src/main/java/org/apache/geode/test/dunit/rules/DistributedExecutorServiceRule.java