String matches regexp [closed]

问题

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.

Closed 9 years ago.

I used perl, unix and java regular expression lot of time, but I'm surprised in java about that:

    "help".matches("^h")  

is false!!

From java documentation: http://docs.oracle.com/javase/8/docs/api/java/lang/String.html#matches-java.lang.String-)

"true if, and only if, this string matches the given regular expression"

     "help".matches("^h.*")

or

     "help".matches("^h.*$")

return of course true.

It's surprising only me?

回答1:

"help" does not macth "^h". Only the first letter in help matches "^h"

回答2:

Java is a bit more strict than say perl or ruby. It's trying to match the entire string and "help" has an extra elp at the end that /^h/ won't match on.

From the docs:

Tells whether or not this string matches the given regular expression.

Not a substring, the whole string.

来源：https://stackoverflow.com/questions/7418924/string-matches-regexp