regex: replace matched text with output of method it's passed to

Question

I have a text file that's marked up like this:

Old McDonald had a <:farm/101:>

When the program reading through this text file hits this tag, it passes farm/101 to a method that converts the tag to appropriate HTML code, depending on what sort of tag is passed. In this case, the word farm needs to be turned into a hyperlink, with 101 as its HREF. This is done in the parseTag() method, which is called as follows:

Pattern pattern = Pattern.compile("<:(.+?):>");        
Matcher tagMatch = pattern.matcher(in);

while (tagMatch.find()) {
    String parsed = parseTag(tagMatch.group(1);
    // replace tagMatch.group(0) with parsed
}

I then want to replace the entire tag with the output of that method. I've thought about doing something like:

Pattern pattern = Pattern.compile("<:");    
String split = pattern.split(in);    
StringBuilder sb = new StringBuilder();
for (int i = 0; i < split.length; i++){
    if (i%2 == 0) sb.append(split[i]);
    else sb.append(parseTag(split[i]);
} 
String final = sb.toString();

final here would give me what I want, but this seems messy..

Pshemo · Accepted Answer · 2013-12-05 21:59:47Z

3

You can use appendReplacement and appendTail methods from Matcher instance.

Try

StringBuffer sb= new StringBuffer();
while (tagMatch.find()) {
    //this will add text to buffer with replaced matched part
    tagMatch.appendReplacement(sb, parseTag(tagMatch.group(1)));
}
tagMatch.appendTail(sb);//to add rest of input after last replacement

String result = sb.toString();
System.out.println(result);

answered Dec 5, 2013 at 21:59

Pshemo

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