question: private static String normalizeHelper ( String number , Map < Character , Character > normalizationReplacements , boolean removeNonMatches ) { StringBuilder normalizedNumber = new StringBuilder ( number . length ( ) ) ; for ( int i = 0 ; i < number . length ( ) ; i ++ ) { char character = number . charAt ( i ) ; Character newDigit = normalizationReplacements . get ( Character . toUpperCase ( character ) ) ; if ( newDigit != null ) { normalizedNumber . append ( newDigit ) ; } else if ( ! removeNonMatches ) { normalizedNumber . append ( character ) ; } } return normalizedNumber . toString ( ) ; }
target:  Normalizes a string of characters representing a phone number by replacing all characters found in the accompanying map with the values therein, and stripping all other characters if removeNonMatches is true.