Question

I am trying to validate the following strings:

org/com[2]/net[4]/uk@name  
org/com[2]/net[4]

Why doesn’t the following regular expression work:

(((.*(\[.*?\])((\/)?)))|(\@(.*)))

Please help.

Answer 1

Why doesn’t the following regular expression work:

Your expression can be broken down to

• (.*(\[.*?\])((\/)?)), or
• (\@(.*))

The former part can be broken down into

• .*, followed by
• \[.*?\] (which is not the same as (\[.*\])?) , possibly followed by
• /

---

Here’s another suggestion:

String part = "[^/\\[\\]]+(\\[\\d*\\])?";
String pattern = String.format("%s(/%<s)*(@.*)?", part);

Test cases:

String[] tests = {
        "org/com[2]/net[4]/uk@name",
        "org/com[2]/net[4]",
        "org/com[2/net",
        "org/com2]/net",
        "org/com[2]/net",
        "org/com[2]/net/",
        "org/com[2]/net@blah",
};

for (String test : tests)
    System.out.println(test + ": " + test.matches(pattern));

Output:

org/com[2]/net[4]/uk@name: true
org/com[2]/net[4]: true
org/com[2/net: false
org/com2]/net: false
org/com[2]/net: true
org/com[2]/net/: false
org/com[2]/net@blah: true