code: private int matchingQuote(int i){
          if(string.charAt(i)!='"')
              throw new UnsupportedOperationException();
  
          ++i;
          boolean escape = false;
          while(i<string.length()){
              char ch = string.charAt(i);
              if(escape)
                  escape = false;
              else if(ch=='\\')
                  escape = true;
              else if(ch=='"')
                  return i;
              ++i;
          }
          throw new IllegalArgumentException("unterminated quoted-string");
      }
docs: /*-------------------------------------------------[ Helper ]---------------------------------------------------