Java正则表达式-仅匹配一次

Question

I have this pattern "[A-Za-z -]*" that I'm using when validating input fields:

if (input.matches("[A-Za-z -]*")) {
   return true;
} else {
   return false;
}

Basically, I'm checking if the inputs are within my field validation requirements (letters, space, and dash (allow one dash only)). My problem is I should return true only if it has letters, space, and dash (ONE DASH only), my current code returns true even if I have inputted a lot of dashes. How can I restrict my pattern to detect if dash exceeds one?

Answer 1

The following is equivalent to your regex, except that it allows at most one dash:

[A-Za-z ]*-?[A-Za-z ]*

This matches zero or more letters/spaces, followed by at most one dash, followed by zero or more letters/spaces.

Answer 2

Start by removing a dash.

if(input.indexOf('-') != 0) input.replaceFirst("-", " ");

Then, since you've only removed one dash, you can run your regex query without checking for hyphens. If one exists, the query will return false.

Answer 3

在输入开始处使用锚定的否定前瞻：

^(?!(.*-){2})[A-Za-z -]*