如何用零字符正则表达式检查Java中的字符串？

Question

The following piece of code checks for same variable portion /en(^$|.*) which is empty or any characters. So the expression should match /en AND /en/bla , /en/blue etc. But the expression doesn't work when checking for just /en .

"/en".matches("/en(^$|.*)")

Is there a way to make this empty regex check (^$) perform with java?

edit

I mean: Is there a way to make this piece of code return true ?

Answer 1

What you're currently doing is checking whether en is followed by the start of string then the end of string (which doesn't make sense, since the start of string needs to be first) or anything else. This should work:

"/en".matches("/en(|.*)")

Or just using ? (optional):

"/en".matches("/en(.*)?")

But it's rather pointless, since * is zero or more (so a blank string will match for .* ), just this should do it:

"/en".matches("/en.*")

EDIT:

Your code was already returning true, but it was not matching the ^$ part, but rather .* (similar to the above).

I should point out that you may as well use startsWith , unless your real data is more complex:

"/en".startsWith("/en")

Answer 2

Is there a way to make this piece of code return true?

 "/en".matches("/en(^$|.*)") 

That code does return true. Just try it!

However, your pattern is unnecessarily complex. Try:

"/en".matches("/en.*")

This will match /en followed by anything (including nothing).