Java 字符串匹配使用可选字符串的正则表达式

Question

I have the following Java String which I need to compare with the regex but these string can consist of the optional values which may be present or not present I need to perform different things based on their availability:

String 1: With serial

uri =  https://myid.com/123/1234567890128/456/1111

String 2: Without Serial

uri = https://myid.com/123/1234567890128

As we can see the incoming string can have the /456/1111 or it may not have. How can I write a single regex function which checks whether it is present or not? I have written a regex but it would work only if the /456/1111 is present:

uri.matches("(http|https)://.*/123/[0-9]{13}.*)")

I tried adding the optional values after looking at some of the answers here something like this:

uri.matches("(http|https)://.*/123/[0-9]{13}+([/456/[0-9]{1,20}]?)")

But for some reason, it does not work. Can someone please help me how can I verify whether there are any strings present in uri /456/1111 or not. I feel like I am missing some small thing.

Answer 1

regex101.com is your friend in this regard.

When looking at your regex on that site , you can see some errors like:

• you have a lone ] at the end which seems off
• and at last your ? at the end targets the wrong group, move it out of the parenthesis.

Something like https?://[^/]+/123/\d{13}(?:/456/\d{1,20})? should work for you.

The good thing about regex101 is that on the right side you see a detailed explanation about your regex, and it highlights exactly which character does what.

Answer 2

Use

^https?:\/\/.*\/123\/[0-9]{1,13}(?:/456/[0-9]{1,20})?$

See proof .

Explanation

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  http                     'http'
--------------------------------------------------------------------------------
  s?                       's' (optional (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  :                        ':'
--------------------------------------------------------------------------------
  \/                       '/'
--------------------------------------------------------------------------------
  \/                       '/'
--------------------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  \/                       '/'
--------------------------------------------------------------------------------
  123                      '123'
--------------------------------------------------------------------------------
  \/                       '/'
--------------------------------------------------------------------------------
  [0-9]{1,13}              any character of: '0' to '9' (between 1
                           and 13 times (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (optional
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    /456/                    '/456/'
--------------------------------------------------------------------------------
    [0-9]{1,20}              any character of: '0' to '9' (between 1
                             and 20 times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )?                       end of grouping
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

Answer 3

The reason the pattern that you tried does not work, is because in the last part of your pattern you have ([/456/[0-9]{1,20}]?) which means:

• ( Capture group
  • [/456/[0-9]{1,20} Match 1-20 repetitions of either / or a digit 0-9 (as 0-9 also matches 456)
  • ]? Match optional ]
• ) Close group

---

What you could do instead, is making the last group as a whole optional without a character class use https? making the s optional.

^https?://.*/123/[0-9]{13}(?:/456/[0-9]{1,20})?$

Regex demo | Java demo

As you use matches() it should match the whole string and you can omit the anchors ^ and $

String uri1 =  "https://myid.com/123/1234567890128/456/1111";
String uri2 = "https://myid.com/123/1234567890128";
String uri3 = "https://myid.com/123/1234567890128/456/111122222222222222222";
String pattern = "https?://.*/123/[0-9]{13}(?:/456/[0-9]{1,20})?";

System.out.println(uri1.matches(pattern));
System.out.println(uri2.matches(pattern));
System.out.println(uri3.matches(pattern));

Output

true
true
false