正则表达式仅允许单词之间使用单个分隔符

Question

I need to construct a regular expression such that it should not allow / at the start or end, and there should not be more than one / in sequence.

Valid Expression is: AB/CD
Valid Expression   :AB
Invalid Expression:  //AB//CD//
Invalid Expression:  ///////
Invalid Expression:  AB////////

The / character is just a separator between two words. Its length should not be more than one between words.

Answer 1

[a-zA-Z]+(/[a-zA-Z]+)+

It matches

a/b
a/b/c
aa/vv/cc

doesn't matches

a
/a/b
a//b
a/b/

Demo

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Reg {
    public static void main(String[] args) {
    Pattern pattern = Pattern.compile("[a-zA-Z]+(/[a-zA-Z]+)+");
    Matcher matcher = pattern.matcher("a/b/c");
    System.out.println(matcher.matches());
    }
}

Answer 2

This regex does it:

^(?!/)(?!.*//).*[^/]$

So in java:

if (str.matches("(?!/)(?!.*//).*[^/]"))

Note that ^ and $ are implied by matches() , because matches must match the whole string to be true.

Answer 3

Assuming you only want to allow alphanumerics (including underscore) between slashes, it's pretty trivial:

boolean foundMatch = subject.matches("\\w+(?:/\\w+)*");

Explanation:

\w+  # Match one or more alnum characters
(?:  # Start a non-capturing group
 /   # Match a single slash
 \w+ # Match one or more alnum characters
)*   # Match that group any number of times