Replace in regex pattern with group from another pattern

Question

I have a string like

a#?.text1

I have two other strings like c#1.text2 and d#2.text3

I want to replace #? in a#?.text1 with a#1.text1 if I choose c#1.text2. If I choose d#2.text3, then I want to replace a#?.text1 with a#2.text1. What is the easiest way to do this? I came up with a solution using groups, but my team doesn't think it is an efficient way of doing it. Here's my Java code:

Pattern strPattern = Pattern.compile("(\\w+)(#\\?)(\\.\\w+)");
Pattern replacePattern = Pattern.compile("(\\w+)(#\\d+)(\\.\\w+)");

Matcher strMatcher = strPattern.matcher("a#?.text1");
Matcher replaceMatcher1 = replacePattern.matcher("c#1.text2");
Matcher replaceMatcher2 = replacePattern.matcher("d#2.text3");

if(strMatcher.matches() && replaceMatcher1.matches()) {
  String number = replaceMatcher1.group(2);
  return strMatcher.replaceAll(strMatcher.group(1) + number + strMatcher.group(3));
} else if(strMatcher.matches() && replaceMatcher2.matches()) {
  String number = replaceMatcher2.group(2);
  return strMatcher.replaceAll(strMatcher.group(1) + number + strMatcher.group(3));
}

The feedback I got was that groups are inefficient and I have to find an easier way to do this.

Is there a better way to do this?

Pushpesh Kumar Rajwanshi · Accepted Answer · 2019-03-31 19:58:37Z

So looks like you just want to extract the number after # from your two strings which are c#1.text2 and d#2.text3 and replace ? just after # in a#?.text1 string.

The code you've written seems a little much where you're created two Pattern and then you're doing replacement using Matcher objects by capturing three groups, where as this can be easily done with some shorter codes without needing to create two Pattern object.

Just extract the number you need to replace and then replace it in the string directly using replaceFirst method on String object itself using these codes,

Pattern replacePattern = Pattern.compile("\\w+#(\\d+)\\.\\w+");
Matcher m = replacePattern.matcher("c#1.text2"); // same way for d#2.text3
if (m.matches()) {
    String digit = m.group(1); // the digit you wanted to extract
    String retVal = "a#?.text1".replaceFirst("(?<=#)\\?", digit); // replace ? preceded by # with the digit using replaceFirst
    System.out.println(retVal); // prints a#1.text1
    return retVal;
} else {
    System.out.println("String doesn't match the pattern");
}

Overall your codes can compactly be written as,

Pattern replacePattern = Pattern.compile("\\w+#(\\d+)\\.\\w+");
Matcher m = replacePattern.matcher("c#1.text2"); // same way for d#2.text3
if (m.matches()) {
    return "a#?.text1".replaceFirst("(?<=#)\\?", m.group(1)); // returns a#1.text1
}

Collectives™ on Stack Overflow

Replace in regex pattern with group from another pattern

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related