iuseavalidatorthatrequiresaregextobespecified.inthecaseofvalidatingagainstanemptystring，id on ' tknowhogeneratesucharegeged
the regex ^ $ matchesonlyemptystrings (I.e.stringsoflength0).here ^ and $ arethebeginingandendofthestringanchors，RESS
ifyouneedtocheckifastringcontainsonlywhitespaces，you can use ^s * $.note thatsistheshorthandforthewhitespacharacter
Finally，in Java，matchesattemptstomatchagainsttheentirestring，soyoucanomittheanchorsshouldyouchooseto。
参考资料
非注册解决方案
youcanalsousestring.isempty (tocheckifastringhaslength0. ifyouwanttoseeifastringcontaingonlywhitespacecharacters，thenyais )