Replace Java Regex Capture Groups with Parts of Themselves

Question

What is the best way in Java for doing the following replacement on Strings:

I have text that looks similar to this:

one two [[**my_word** other words]] three four [[**my_other_word** other words]] five six

and I want the following text

one two **my_word** three four **my_other_word** five six

I tried using regex capture groups but how can I replace one capture group with another one?

each group have a number $1, $2, $3 ... Then u can use it. $1 = group 1 captured, example $1 = potato => "hi $1" (hi potato). — Eduardo Lynch Araya
– Eduardo Lynch Araya, Commented Jan 31, 2017 at 15:36
I got stuck when I tried using the Java Pattern and Matcher API. — xgb84j
– xgb84j, Commented Jan 31, 2017 at 15:47
I added an example of how to use the Pattern and Matcher objects if you are interested in seeing how it could be done. — Falle1234
– Falle1234, Commented Jan 31, 2017 at 15:50

JF Meier · Accepted Answer · 2017-01-31 15:37:33Z

3

Use

https://www.tutorialspoint.com/java/java_string_replaceall.htm

and do something like

a.replaceAll("\\[\\[(\\w+)[^\\[]+\\]\\]", "$1");

answered Jan 31, 2017 at 15:37

JF Meier

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Falle1234 · Accepted Answer · 2017-01-31 15:47:18Z

1

Depending on what your needs are, you could either use a oneliner like

a.replaceAll("\\[\\[(\\*\\*\\w+\\*\\*).*?\\]\\]", "$1");

Or the more complicated version where you can control what to replace each match with.

String inputString = "one two [[**my_word** other words]] three four [[**my_other_word** other words]] five six";
Pattern pattern = Pattern.compile("\\[\\[(\\*\\*\\w+\\*\\*).*?\\]\\]", Pattern.DOTALL);
Matcher matcher = pattern.matcher(inputString);
StringBuffer outputBuffer = new StringBuffer();
while (matcher.find()) {
    String match = matcher.group(1);        
    matcher.appendReplacement(outputBuffer, match);
}
matcher.appendTail(outputBuffer);

String output = outputBuffer.toString();

answered Jan 31, 2017 at 15:47

Falle1234

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Comments

m_callens · Accepted Answer · 2017-01-31 17:55:42Z

1

a.replaceAll("\\[\\[(\\*\\*\\w+\\*\\*)(?:\\s\\w+\\s?)+\\]\\]", "$1");

edited Jan 31, 2017 at 17:55

answered Jan 31, 2017 at 15:39

m_callens

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5 Comments

Falle1234 Over a year ago

The single backslashes you are using are not valid as regex escape characters in java. They need to be double backslashes.

NathanOliver Over a year ago

Hey I just wanted to ping you on your last C++ question. You had an off by on error. std::vector<std::string> base(values->begin() + 1, values->begin() + 4); only gives you the first 3 elements. You need to change the 4 to a 5 to get the first 4 elements.

m_callens Over a year ago

@NathanOliver ah, I knew it would be a stupid mistake. Didn't know if it was inclusive or exclusive ending bounds. Thanks!

NathanOliver Over a year ago

@m_callens No problem. Generally then end is never included in the range copied.

Joe C Over a year ago

While you may have solved this user's problem, code-only answers are not very helpful to users who come to this question in the future. Please edit your answer to explain why your code solves the original problem.

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