question: private void initPattern ( ) { StringBuffer patternTemplateRegex = new StringBuffer ( ) ; logger . debug ( "Get placeholder matcher" ) ; Matcher placeholderMatcher = getPlaceholderMatcher ( ) ; logger . debug ( "Replace all placeholder with regex group capture" ) ; while ( placeholderMatcher . find ( ) ) { String group = placeholderMatcher . group ( 1 ) ; if ( ! groups . contains ( group ) ) { logger . trace ( "New group found, add it, replace with a capture group" ) ; groups . add ( group ) ; String groupRegex = getGroupRegex ( group ) ; placeholderMatcher . appendReplacement ( patternTemplateRegex , Matcher . quoteReplacement ( "(?<" + group + ">" + groupRegex + ")" ) ) ; } else { logger . trace ( "Existing group found, replace with a back reference" ) ; placeholderMatcher . appendReplacement ( patternTemplateRegex , Matcher . quoteReplacement ( "\\k<" + group + ">" ) ) ; } } placeholderMatcher . appendTail ( patternTemplateRegex ) ; String patternRegex = patternTemplateRegex . toString ( ) ; logger . debug ( "pattern:" + patternRegex ) ; pattern = Pattern . compile ( patternRegex ) ; }
target:  Initialize the pattern to match files.