Question

I am a noob to regex.

I have string like:-

String str = "sbs 01.00 sip ${dreamworks.values} print ${fwVer} to 
              used ${lang} en given ${model}  in ${region}";

and
i have to extract all patterns matched with this type ${….}

Like:- for given str result should be

${dreamworks.values} 
${fwVer}   
${lang}
${model}
${region}

further if it finds any duplicates then gives only one .
for ex:-

String feed = "sip ${dreamworks.values} print ${fwVer} to ${fwVer} used
                ${lang} en ${lang}given ${model}  in ${region}"

result should be:-

 ${dreamworks.values}  
 ${fwVer}   
 ${lang}
 ${model}
 ${region}  

only

this is my answer:-

PLACEHOLDER_PATTERN = "\\$\\{\\w+\\}";

but this one not giving the correct result.
it gives only

${fwVer}
${lang}
${model}
${region}

So please suggest me correct regex.

Answer 1

You are not considering the . in between the word. \\w does not include the dot(.).

You need to change your pattern to: –

PLACEHOLDER_PATTERN = "\\$\\{.+?\\}";

dot(.) matches everything, and that is what you want right?

Also, I have used here reluctant quantifier – .+? so that it only matches the first } after {, since if you use a greedy quantifier (.+), dot(.) will also match the } in the way till it finds the last }.

---

UPDATE: –

To get just the unique values, you can use this pattern: –

"(\\$\\{[^}]+\\})(?!.*?\\1)"

It will match only those pattern, which is not followed by the string containing the same pattern.

NOTE: – Here, I have used [^}], in place of .+?. It will match any character except }. So, now in this case, you don’t need a reluctant quantifier.

\1 is used for backreferencing, but we need to escape it with a backslash, and hence \\1, and (?!...) is used for negative look ahead.