Java regex for matching certain parts of JSON substrings

Question

I am trying to write a regex that looks for strings with the following pattern:

Begin with an opening bracket { followed by a double-quote "
Then allows for a string of 1+ alphanumeric characters a-zA-Z0-9
Then another double-quote " followed by a colon : and an opening brace [
Then allows for any string of 0+ alphanumeric characters a-zA-Z0-9

So some strings that would match the regex:

{"hello":[blah
{"hello":[
{"1":[

And some strings that would not match:

{hello:[blah
hello":[
{"2:[

So far, the best I've been able to come up with is:

String regex = "{\"[a-zA-Z0-9]+\":\[[a-zA-Z0-9]*";
if(myString.matches(regex))
    // do something

But I know I'm way off base. Can any regex gurus help reel me in? Thanks in advance!

If I am to believe the online regex tester this should work, unless of course there is some Java specifics I'm missing. — atomman
– atomman, Commented Jan 23, 2013 at 16:18
Nikolay - I've already stripped out all whitespace prior to this code being executed. jlordo - good call on the parser, but it feels like its overkill for this simple use case, but I definitely would use a parser if it become more complex than this. — IAmYourFaja
– IAmYourFaja, Commented Jan 23, 2013 at 16:23
You have a compiler error (invalid escape sequence). See Ian Roberts' answer. In cases like this, always include the complete error message in your question. See the stackoverflow question checklist — jlordo
– jlordo, Commented Jan 23, 2013 at 16:23

Ian Roberts · Accepted Answer · 2013-01-23 16:20:41Z

5

String regex = "{\"[a-zA-Z0-9]+\":\[[a-zA-Z0-9]*";

The problem here is that you need an extra backslash before the square bracket. This is because you need the regex to contain \[ in order to match a square bracket, which means the string literal needs to contain \\[ to escape the backslash for the Java code parser. Similarly, you may also need to escape the { in the regex as it is a metacharacter (for bounded repetition counts)

String regex = "\\{\"[a-zA-Z0-9]+\":\\[[a-zA-Z0-9]*";

answered Jan 23, 2013 at 16:20

Ian Roberts

123k17 gold badges177 silver badges191 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Java regex for matching certain parts of JSON substrings

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related