使用正则表达式查找字符串中的子字符串-JAVA

Question

Suppose i have a string " kk abcjkmkc jjkocc abc jjj 'abckkkkkkkkkkkkkkkk ' "

I want to replace the substring abc 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()
 `

Answer 1

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, eg 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.

fixed to put "reluctant" qualifier after second * , so that the first abc will be found.

If you want to replace the substring you find, it gets trickier. The above pattern matches the entire beginning of the string up through abc , and I couldn't get a look-behind to work so that the match would be only the abc 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.

Answer 2

使用以下模式： a\\.b\\.c(?=(([^']*'){2})*[^']*$) 演示

Answer 3

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