public static int calculateLuhnChecksum(long num){ if(num< 0){ throw new IllegalArgumentException("Non-negative numbers only."); } final var numStr=String.valueOf(num); var sum=0; var isOddPosition=true; // We loop on digits in numStr from right to left. for(var i=numStr.length(...
length()) { throw new IllegalArgumentException("Invalid code point: " + codePoint); } return CODE_POINTS.charAt(codePoint); } public static int numberOfValidInputCharacters() { return CODE_POINTS.length(); } /** * Helper method to calculate the sum for both check character generation and...