public static void clearThreadLocal(ThreadLocal tl) {
ThreadGroup root = Thread.currentThread().getThreadGroup().getParent();
while (root.getParent() != null) {
root = root.getParent();
}
visit(root, tl, 0);
}
private static void visit(ThreadGroup group, ThreadLocal tl, int level) {
// Get threads in `group'
int numThreads = group.activeCount();
Thread[] threads = new Thread[numThreads * 2];
numThreads = group.enumerate(threads, false);
// Enumerate each thread in `group'
for (int i = 0; i < numThreads; i++) {
Thread thread = threads[i];
clearThreadLocal(tl, thread);
}
// Get thread subgroups of `group'
int numGroups = group.activeGroupCount();
ThreadGroup[] groups = new ThreadGroup[numGroups * 2];
numGroups = group.enumerate(groups, false);
// Recursively visit each subgroup
for (int i = 0; i < numGroups; i++) {
visit(groups[i], tl, level + 1);
}
}