How to judge null for different types of fields, sets, lists / sets / maps, and objects

String type ：stringutils.isblank("xxx")

It can be judged whether it is null, Is it "", Is it an empty string ( There is a space between the quotes ) Such as ： " "

Object type ： objects.isNull(User) and objects.nonNull(User)

You can judge the blank of the object , amount to user==null,Java8 Introduced in lambda after , So there are many such filter(Objects::isNull) This way of writing , Obviously than filter(x -> x == null). The method is more intuitive .

List/Set type ：CollectionUtils.isEmpty() and CollectionUtils.isNotEmpty

Method can check null And length 0 Of list/set

 Map type ：MapUtils.isEmpty(map) and MapUtils.isNotEmpty(map)