public static int sizeOf(Map<?, ?> map) {
        if (map == null) {
            return 0;
        }
        return map.size();
    }
@author Robert HG (254963746@qq.com) on 6/23/14.
lts-core/src/main/java/com/github/ltsopensource/core/commons/utils/CollectionUtils.java