CompleteFuture的实现原理

public static <K> Boolean getBoolean(final Map<? super K, ?> map, final K key) {
        if (map != null) {
            final Object answer = map.get(key);
            if (answer != null) {
                if (answer instanceof Boolean) {
                    return (Boolean) answer;
                }
                if (answer instanceof String) {
                    return Boolean.valueOf((String) answer);
                }
                if (answer instanceof Number) {
                    final Number n = (Number) answer;
                    return n.intValue() != 0 ? Boolean.TRUE : Boolean.FALSE;
                }
            }
        }
        return null;
    }