static bool removeAll(Collection a, Collection b) {
ret a != null && b != null && a.removeAll(b);
}
static void removeAll(Map a, Collection b) {
if (a != null && b != null)
for (A x : b)
a.remove(x);
}
static bool removeAll(Collection c, B... b) {
ret c != null && b != null && c.removeAll(Arrays.asList(b));
}
static void removeAll(Map a, A... b) {
if (a != null && b != null)
for (A x : b)
a.remove(x);
}