|
| 1 | +packageOthers; |
| 2 | + |
| 3 | +importjava.util.Objects; |
| 4 | + |
| 5 | +/** |
| 6 | + * Damm algorithm is a check digit algorithm that detects all single-digit errors |
| 7 | + * and all adjacent transposition errors. It was presented by H. Michael Damm in 2004. |
| 8 | + * Essential part of the algorithm is a quasigroup of order 10 |
| 9 | + * (i.e. having a 10 × 10 Latin square as the body of its operation table) |
| 10 | + * with the special feature of being weakly totally anti-symmetric. |
| 11 | + * Damm revealed several methods to create totally anti-symmetric quasigroups |
| 12 | + * of order 10 and gave some examples in his doctoral dissertation. |
| 13 | + * |
| 14 | + * @see <a href="https://en.wikipedia.org/wiki/Damm_algorithm">Wiki. Damm algorithm</a> |
| 15 | + */ |
| 16 | +publicclassDamm { |
| 17 | + |
| 18 | +/** |
| 19 | + * Weakly totally anti-symmetric quasigroup of order 10. |
| 20 | + * This table is not the only possible realisation of weak totally anti-symmetric |
| 21 | + * quasigroup but the most common one (taken from Damm doctoral dissertation). |
| 22 | + * All zeros lay on the diagonal because it simplifies the check digit calculation. |
| 23 | + */ |
| 24 | +privatestaticfinalbyte[][]DAMM_TABLE = { |
| 25 | + {0,3,1,7,5,9,8,6,4,2}, |
| 26 | + {7,0,9,2,1,5,4,8,6,3}, |
| 27 | + {4,2,0,6,8,7,1,3,5,9}, |
| 28 | + {1,7,5,0,9,8,3,4,2,6}, |
| 29 | + {6,1,2,3,0,4,5,9,7,8}, |
| 30 | + {3,6,7,4,2,0,9,5,8,1}, |
| 31 | + {5,8,6,9,7,2,0,1,3,4}, |
| 32 | + {8,9,4,5,3,6,2,0,1,7}, |
| 33 | + {9,4,3,8,6,1,7,2,0,5}, |
| 34 | + {2,5,8,1,4,3,6,7,9,0} |
| 35 | + }; |
| 36 | + |
| 37 | +/** |
| 38 | + * Check input digits by Damm algorithm. |
| 39 | + * |
| 40 | + * @param digits input to check |
| 41 | + * @return true if check was successful, false otherwise |
| 42 | + * @throws IllegalArgumentException if input parameter contains not only digits |
| 43 | + * @throws NullPointerException if input is null |
| 44 | + */ |
| 45 | +publicstaticbooleandammCheck(Stringdigits) { |
| 46 | +checkInput(digits); |
| 47 | +int[]numbers =toIntArray(digits); |
| 48 | + |
| 49 | +intchecksum =0; |
| 50 | +for (intnumber :numbers) { |
| 51 | +checksum =DAMM_TABLE[checksum][number]; |
| 52 | + } |
| 53 | + |
| 54 | +returnchecksum ==0; |
| 55 | + } |
| 56 | + |
| 57 | +/** |
| 58 | + * Calculate check digit for initial digits and add it tho the last position. |
| 59 | + * |
| 60 | + * @param initialDigits initial value |
| 61 | + * @return digits with the checksum in the last position |
| 62 | + * @throws IllegalArgumentException if input parameter contains not only digits |
| 63 | + * @throws NullPointerException if input is null |
| 64 | + */ |
| 65 | +publicstaticStringaddDammChecksum(StringinitialDigits) { |
| 66 | +checkInput(initialDigits); |
| 67 | +int[]numbers =toIntArray(initialDigits); |
| 68 | + |
| 69 | +intchecksum =0; |
| 70 | +for (intnumber :numbers) { |
| 71 | +checksum =DAMM_TABLE[checksum][number]; |
| 72 | + } |
| 73 | + |
| 74 | +returninitialDigits +checksum; |
| 75 | + } |
| 76 | + |
| 77 | +publicstaticvoidmain(String[]args) { |
| 78 | +System.out.println("Damm algorithm usage examples:"); |
| 79 | +varvalidInput ="5724"; |
| 80 | +varinvalidInput ="5824"; |
| 81 | +checkAndPrint(validInput); |
| 82 | +checkAndPrint(invalidInput); |
| 83 | + |
| 84 | +System.out.println("\nCheck digit generation example:"); |
| 85 | +varinput ="572"; |
| 86 | +generateAndPrint(input); |
| 87 | + } |
| 88 | + |
| 89 | +privatestaticvoidcheckAndPrint(Stringinput) { |
| 90 | +StringvalidationResult =Damm.dammCheck(input) |
| 91 | + ?"valid" |
| 92 | + :"not valid"; |
| 93 | +System.out.println("Input '" +input +"' is " +validationResult); |
| 94 | + } |
| 95 | + |
| 96 | +privatestaticvoidgenerateAndPrint(Stringinput) { |
| 97 | +Stringresult =addDammChecksum(input); |
| 98 | +System.out.println("Generate and add checksum to initial value '" +input +"'. Result: '" +result +"'"); |
| 99 | + } |
| 100 | + |
| 101 | +privatestaticvoidcheckInput(Stringinput) { |
| 102 | +Objects.requireNonNull(input); |
| 103 | +if (!input.matches("\\d+")) { |
| 104 | +thrownewIllegalArgumentException("Input '" +input +"' contains not only digits"); |
| 105 | + } |
| 106 | + } |
| 107 | + |
| 108 | +privatestaticint[]toIntArray(Stringstring) { |
| 109 | +returnstring.chars() |
| 110 | + .map(i ->Character.digit(i,10)) |
| 111 | + .toArray(); |
| 112 | + } |
| 113 | +} |