fix: Changes Requested Done

* Removed the extra empty lines * Respected the alphabetical order of the README.md file and insert Luhn Mod N to the correct position * Checked the code duplication reported by Sonar
iluwatar · Dec 8, 2024 · 758ab02 · 758ab02
1 parent 2900bfc
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diff --git a/README.md b/README.md
@@ -279,6 +279,97 @@ public class LinearSearchSnippet {
   }
 }
 ```
+### Luhn Mod N
+
+
+```java
+public class LuhnModnSnippet {
+
+  private static final String CODE_POINTS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+  /**
+   * Generates a check character using the Luhn mod N algorithm.
+   *
+   * @param character the input string consisting of valid alphanumeric characters
+   * @return the generated check character
+   * @throws IllegalArgumentException if the input contains invalid characters
+   */
+  public static int codePointFromCharacter(char character) {
+    if (CODE_POINTS.indexOf(character) == -1) {
+      throw new IllegalArgumentException("Invalid character: " + character);
+    }
+    return CODE_POINTS.indexOf(character);
+  }
+
+  /**
+   * Converts a code point to its corresponding character.
+   *
+   * @param codePoint the code point to be converted
+   * @return the character representation of the code point
+   * @throws IllegalArgumentException if the code point is out of range.
+   */
+  public static char characterFromCodePoint(int codePoint) {
+    if (codePoint < 0 || codePoint >= CODE_POINTS.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 validation.
+   *
+   * @param input the input string
+   * @param factorStart the initial factor to start with (1 or 2)
+   * @return the calculated sum, reminder, and the numberOfValidInputCharacters
+   */
+  private static int[] calculateSum(String input, int factorStart) {
+    if (input == null || input.isEmpty()) {
+      throw new IllegalArgumentException("Input cannot be empty");
+    }
+
+    int factor = factorStart;
+    int sum = 0;
+    int n = numberOfValidInputCharacters();
+
+    for (int i = input.length() - 1; i >= 0; i--) {
+      int codePoint = codePointFromCharacter(input.charAt(i));
+      int addend = factor * codePoint;
+      factor = (factor == 2) ? 1 : 2;
+      addend = (addend / n) + (addend % n);
+      sum += addend;
+    }
+    return new int[]{sum, sum % n, n};
+  }
+
+  /**
+   * Generates a check character for the given input string using the Luhn mod N algorithm.
+   *
+   * @param input the input string (non-empty)
+   * @return the generated check character
+   * @throws IllegalArgumentException if the input is null or empty
+   */
+  public static char generateCheckCharacter(String input) {
+    int[] result = calculateSum(input, 2);
+    return characterFromCodePoint((result[2] - result[1]) % result[2]);
+  }
+
+  /**
+   * Validates a check character by applying the Luhn mod N algorithm.
+   *
+   * @param input the input string (including the check character)
+   * @return true if the input passes validation, false otherwise
+   * @throws IllegalArgumentException if the input is null or empty
+   */
+  public static boolean validateCheckCharacter(String input) {
+    int[] result = calculateSum(input, 1);
+    return (result[1] == 0);
+  }
+}
+```
 
 ### Merge Sort
 
@@ -435,134 +526,6 @@ public class SieveOfEratosthenesSnippet {
   }
 }
 ```
-### Luhn Mod N
-
-
-```java
-public class LuhnModnSnippet {
-
-
-  private LuhnModnSnippet() {
-    throw new IllegalStateException("LuhnModnSnippet class");
-  }
-
-
-  private static final String CODE_POINTS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
-
-
-  /**
-   * Generates a check character using the Luhn mod N algorithm.
-   *
-   * @param character the input string consisting of valid alphanumeric characters
-   * @return the generated check character
-   * @throws IllegalArgumentException if the input contains invalid characters
-   */
-  public static int codePointFromCharacter(char character) {
-    int index = CODE_POINTS.indexOf(character);
-    if (index == -1) {
-      throw new IllegalArgumentException("Invalid character: " + character);
-    }
-    return index;
-  }
-
-
-  /**
-   * Converts a code point to its corresponding character.
-   *
-   * @param codePoint the code point to be converted
-   * @return the character representation of the code point
-   * @throws IllegalArgumentException if the code point is out of range.
-   */
-  public static char characterFromCodePoint(int codePoint) {
-    if (codePoint < 0 || codePoint >= CODE_POINTS.length()) {
-      throw new IllegalArgumentException("Invalid code point: " + codePoint);
-    }
-    return CODE_POINTS.charAt(codePoint);
-  }
-
-
-  public static int numberOfValidInputCharacters() {
-    return CODE_POINTS.length();
-  }
-
-
-  /**
-   * Generates a check character for the given input string using the Luhn mod N algorithm.
-   *
-   * @param input the input string (non-empty)
-   * @return the generated check character
-   * @throws IllegalArgumentException if the input is null or empty
-   */
-  public static char generateCheckCharacter(String input) {
-    if (input == null || input.isEmpty()) {
-      throw new IllegalArgumentException("Input cannot be empty");
-    }
-
-
-    int factor = 2;
-    int sum = 0;
-    int n = numberOfValidInputCharacters();
-
-
-    for (int i = input.length() - 1; i >= 0; i--) {
-      int codePoint = codePointFromCharacter(input.charAt(i));
-      int addend = factor * codePoint;
-
-
-      factor = (factor == 2) ? 1 : 2;
-
-
-      addend = (addend / n) + (addend % n);
-      sum += addend;
-    }
-
-
-    int remainder = sum % n;
-    int checkCodePoint = (n - remainder) % n;
-
-
-    return characterFromCodePoint(checkCodePoint);
-  }
-
-
-  /**
-   * Validates a check character by applying the Luhn mod N algorithm.
-   *
-   * @param input the input string (including the check character)
-   * @return true if the input passes validation, false otherwise
-   * @throws IllegalArgumentException if the input is null or empty
-   */
-  public static boolean validateCheckCharacter(String input) {
-    if (input == null || input.isEmpty()) {
-      throw new IllegalArgumentException("Input cannot be empty");
-    }
-
-
-    int factor = 1;
-    int sum = 0;
-    int n = numberOfValidInputCharacters();
-
-
-    for (int i = input.length() - 1; i >= 0; i--) {
-      int codePoint = codePointFromCharacter(input.charAt(i));
-      int addend = factor * codePoint;
-
-
-      factor = (factor == 2) ? 1 : 2;
-
-
-      addend = (addend / n) + (addend % n);
-      sum += addend;
-    }
-
-
-    int remainder = sum % n;
-
-
-    return (remainder == 0);
-  }
-}
-```
 
 ## Array
 

diff --git a/src/main/java/algorithm/LuhnModnSnippet.java b/src/main/java/algorithm/LuhnModnSnippet.java
@@ -22,24 +22,15 @@
  * SOFTWARE.
  */
 
-
 package algorithm;
 
-
 /**
  * LuhnModnSnippet.
  */
 public class LuhnModnSnippet {
 
-
-  private LuhnModnSnippet() {
-    throw new IllegalStateException("LuhnModnSnippet class");
-  }
-
-
   private static final String CODE_POINTS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
-
   /**
    * Generates a check character using the Luhn mod N algorithm.
    *
@@ -48,14 +39,12 @@ private LuhnModnSnippet() {
    * @throws IllegalArgumentException if the input contains invalid characters
    */
   public static int codePointFromCharacter(char character) {
-    int index = CODE_POINTS.indexOf(character);
-    if (index == -1) {
+    if (CODE_POINTS.indexOf(character) == -1) {
       throw new IllegalArgumentException("Invalid character: " + character);
     }
-    return index;
+    return CODE_POINTS.indexOf(character);
   }
 
-
   /**
    * Converts a code point to its corresponding character.
    *
@@ -70,50 +59,47 @@ public static char characterFromCodePoint(int codePoint) {
     return CODE_POINTS.charAt(codePoint);
   }
 
-
   public static int numberOfValidInputCharacters() {
     return CODE_POINTS.length();
   }
 
-
   /**
-   * Generates a check character for the given input string using the Luhn mod N algorithm.
+   * Helper method to calculate the sum for both check character generation and validation.
    *
-   * @param input the input string (non-empty)
-   * @return the generated check character
-   * @throws IllegalArgumentException if the input is null or empty
+   * @param input the input string
+   * @param factorStart the initial factor to start with (1 or 2)
+   * @return the calculated sum, reminder, and the numberOfValidInputCharacters
    */
-  public static char generateCheckCharacter(String input) {
+  private static int[] calculateSum(String input, int factorStart) {
     if (input == null || input.isEmpty()) {
       throw new IllegalArgumentException("Input cannot be empty");
     }
 
-
-    int factor = 2;
+    int factor = factorStart;
     int sum = 0;
     int n = numberOfValidInputCharacters();
 
-
     for (int i = input.length() - 1; i >= 0; i--) {
       int codePoint = codePointFromCharacter(input.charAt(i));
       int addend = factor * codePoint;
-
-
       factor = (factor == 2) ? 1 : 2;
-
-
       addend = (addend / n) + (addend % n);
       sum += addend;
     }
-
-
-    int remainder = sum % n;
-    int checkCodePoint = (n - remainder) % n;
-
-
-    return characterFromCodePoint(checkCodePoint);
+    return new int[]{sum, sum % n, n};
   }
 
+  /**
+   * Generates a check character for the given input string using the Luhn mod N algorithm.
+   *
+   * @param input the input string (non-empty)
+   * @return the generated check character
+   * @throws IllegalArgumentException if the input is null or empty
+   */
+  public static char generateCheckCharacter(String input) {
+    int[] result = calculateSum(input, 2);
+    return characterFromCodePoint((result[2] - result[1]) % result[2]);
+  }
 
   /**
    * Validates a check character by applying the Luhn mod N algorithm.
@@ -123,32 +109,7 @@ public static char generateCheckCharacter(String input) {
    * @throws IllegalArgumentException if the input is null or empty
    */
   public static boolean validateCheckCharacter(String input) {
-    if (input == null || input.isEmpty()) {
-      throw new IllegalArgumentException("Input cannot be empty");
-    }
-
-
-    int factor = 1;
-    int sum = 0;
-    int n = numberOfValidInputCharacters();
-
-
-    for (int i = input.length() - 1; i >= 0; i--) {
-      int codePoint = codePointFromCharacter(input.charAt(i));
-      int addend = factor * codePoint;
-
-
-      factor = (factor == 2) ? 1 : 2;
-
-
-      addend = (addend / n) + (addend % n);
-      sum += addend;
-    }
-
-
-    int remainder = sum % n;
-
-
-    return (remainder == 0);
+    int[] result = calculateSum(input, 1);
+    return (result[1] == 0);
   }
-}
+}