@Override public long put(long key, long value) {
        assert value != nullValue : "put() called with null-sentinel value " + nullValue;
        SlotAssignmentResult slot = hsa.ensure(key);
        long result;
        if (!slot.isNew()) {
            result = mem.getLong(slot.address());
        } else {
            result = nullValue;
        }
        mem.putLong(slot.address(), value);
        return result;
    }
@Test(expected = AssertionError.class)
    @RequireAssertEnabled
    public void test_put_invalidValue() {
        map.put(newKey(), MISSING_VALUE);
    }