Replace comma in parentheses using regex in java

Question

I want to replace comma when its inside parentheses only.

For Example

 Progamming languages (Java, C#, Perl)

TO

Progamming languages (Java or C# or Perl)

but it should not repace comma in following string

Progamming languages Java, C#, Perl

CODE

It will replace correctly but its not matching up.

 String test  = "Progamming languages (Java, C#, Perl)";
 String test1 = "Progamming languages Java, C#, Perl"


 String foo = replaceComma(test);
 String foo1 = replaceComma(test1);


 private static String replaceComma(String test)
 {
    String patternStr= "\\((?:.*)(,)(?:.*)\\)";
    Pattern pattern = Pattern.compile(patternStr);
    Matcher matcher= pattern.matcher(test);

    if(matcher.matches())
    {
      return  test.replaceAll("(,)", " or ");
    }

    return  test;

 }

UPDATE

String.replaceAll("(,)", " or "); will not work when you have string like this

String test = "Learning, languages (Java, C#, Perl)";

so you have to use @polygenelubricants code

Answer 1

Your error is using matches instead of find here:

if (matcher.find())

From the documentation:

• The matches method attempts to match the entire input sequence against the pattern.
• The find method scans the input sequence looking for the next subsequence that matches the pattern.

But your code also simplifies the issue somewhat - it replaces all commas even if only one of them is in parentheses. It's probably not a good idea to use regular expressions for this sort of task.

Instead you could scan the string one character at a time and count how many pairs of parentheses you are inside. When you see a ( increase the count, and when you see a ) decrease the count. If you see a , then check if the current count is zero.

Answer 2

Another approach is to use positive lookahead and positive lookbehind in your regular expression. That way you can search for commas that occur after a '(', but before a ')'.

(?=X) positive lookahead

(?<=X) positive lookbehind

Mark is correct you need a loop instead of replaceAll. But you can still use a regular expression using the technique I've described.

Answer 3

You can use positive lookahead (?=…) like this:

    String COMMA_INSIDE = ",(?=[^()]*\\))";
    String text = "a, b, c, (d, e, f), g, h, (i, j, k)";
    System.out.println(
        text.replaceAll(COMMA_INSIDE, " OR")
    );
    // a, b, c, (d OR e OR f), g, h, (i OR j OR k)

This matches a comma, but only if the first parenthesis to its right is of the closing kind.

The [^…] is a negated character class. [^()] matches anything but parentheses. The * is zero-or-more repetition. The \) (written as "\\)" as a Java string literal) matches a closing parenthesis, literally. The backslash escapes what is otherwise a special metacharacter for grouping.

This assumes that the input string is well-formed, i.e. parentheses are always balanced and not nested.

Answer 4

String  replaceComma(String input)
{
 String[] strSplit=input.split("[\\(\\)]");
  if(strSplit.length==2)
   input=input.replaceAll(", "," or ");
 return input;
}

UPDATE: For String's like "Learning, languages (Java, C#, Perl)"

String  replaceComma(String input)
{
String[] splitStr=input.split("[\\(\\)]");
 if(splitStr.length==2)
   input=input.replace(splitStr[1],splitStr[1].replaceAll(", ", " or "));
return input;
}