CODEWITHSUNDEEP
javaregex
user3275944
user3275944

Reputation: 57

Find a subtring in a string using a regular expression - JAVA

Suppose i have a string " kk a.b.cjkmkc jjkocc a.b.c. jjj 'a.b.ckkkkkkkkkkkkkkkk ' "

I want to replace the substring a.b.c in the string which are only outside the single quote , but it is not working.

Here is my code `

String str = " kk a.b.cjkmkc  jjkocc a.b.c. jjj 'a.b.ckkkkkkkkkkkkkkkk ' ";
 Pattern p = Pattern.compile("a\\.b\\.c");
 Matcher m = p.matcher(str); 
 int x = m.find()
 `

Upvotes: 1

Views: 348

Answers (3)

ajb
ajb

Reputation: 31699

To search for a substring outside quotes, you can do something like this:

Pattern pat = Pattern.compile("^(?:[^']|'[^']*')*?a\\.b\\.c");

The first part will skip over:

every character that isn't a quote mark ([^']), or

every sequence of non-quote-mark characters enclosed in quotes ('[^']*').

Once those are skipped, then if it sees the pattern you want, it will know that it isn't inside quote marks.

This will handle a simple case. If things start getting more complicated, e.g. you want to allow \' to quote a quote mark in your input string the way C or Java does in a string literal, the regex starts getting more complicated, and you can quickly reach a point whether either your regex is unreadable or regexes aren't suitable solutions.

EDIT: fixed to put "reluctant" qualifier after second *, so that the first a.b.c will be found.

EDIT 2: If you want to replace the substring you find, it gets trickier. The above pattern matches the entire beginning of the string up through a.b.c, and I couldn't get a look-behind to work so that the match would be only the a.b.c part. I think you'll need to put the beginning of the string in a group, and then use $1 in the replacement string to copy the beginning:

Pattern pat = Pattern.compile("^((?:[^']|'[^']*')*?)a\\.b\\.c");
Matcher m = pat.matcher(source);
if (m.find()) {
    result = m.replaceFirst("$1replacement");
}

I'm not sure replaceAll works with this, so if you want to replace all of them, you may need to loop.

Upvotes: 1

TheLostMind
TheLostMind

Reputation: 36304

I wouldn't mess with REGEX. 

public static void main(String[] args) {

    String str = " kk a.b.cjkmkc  jjkocc a.b.c. jjj 'a.b.ckkkkkkkkkkkkkkkk ' ";
    String[] s = str.split("'");
    str = s[0].replaceAll("[abc]", "") + "'"+ s[1]+"'"
            + s[2].replaceAll("[abc]", "");

    System.out.println(str);
}

OP: 

kk ..jkmk  jjko ... jjj 'a.b.ckkkkkkkkkkkkkkkk '

Inefficient.. but works

Upvotes: 0

alpha bravo
alpha bravo

Reputation: 7948

use this pattern : a\.b\.c(?=(([^']*'){2})*[^']*$) Demo

Upvotes: 1

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