string.replaceAll java doesn't work with lookaround regex?

Question

I have a json string like this:

string = "{name={first=sam, last=vo}, hobbies={hobby1=football, hobby2=swimming}}"

And I want to remove the "name=" and the "hobbies=", so that I use this pattern: \w*\=(?={) ->tested using editPadPro

However, when I use the replace all in java:

String pattern = "\\w*\\=(?={)";
String removedParent = string.replaceAll(pattern, "");

I got this error message

"Exception in thread "main" java.util.regex.PatternSyntaxException: Illegal repetition near index 7
\w*\=(?={)"

Can you please give me some advices to get this work?

Regards,

Sam

Do you want to remove other names like "first=, last=, hobby1=,hobby2=" or only the top level names? — 18bytes
– 18bytes, Commented Jul 17, 2012 at 8:33

npinti · Accepted Answer · 2012-07-17 08:36:02Z

4

The problem is that the { character is a special character in regex syntax which denotes an amount (for instance \d{2} denotes 2 digits). In your case, you want to match the literal {, meaning that you need to escape the { character, so you need to change your regex to this: "\\w*\\=(?=\\{)";.

For me, this yielded:

{{first=sam, last=vo}, {hobby1=football, hobby2=swimming}}

answered Jul 17, 2012 at 8:36

npinti

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arthur · Accepted Answer · 2012-07-17 08:39:31Z

1

java.util.regex.PatternSyntaxException: Illegal repetition

comes because of your "{" in "\\w*\\=(?={)". "{" and "}" are special characters to state characters repetitions as you might know ...

just try to escape it like that "\\w*\\=(?=\\{)". and since you're working with json , please consider using a JSON-Parser like:

answered Jul 17, 2012 at 8:39

arthur

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