Remove main function, improve docstring, add JUnit tests for KrishnamurthyNumber. (#5881)

Author: Tanmay-Singh3004

DIRECTORY.md

@@ -982,6 +982,7 @@
             * [JosephusProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/JosephusProblemTest.java)
             * [KaprekarNumbersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KaprekarNumbersTest.java)
             * [KaratsubaMultiplicationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KaratsubaMultiplicationTest.java)
+            * [KrishnamurthyNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KrishnamurthyNumberTest.java)
             * [LeastCommonMultipleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LeastCommonMultipleTest.java)
             * [LeonardoNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LeonardoNumberTest.java)
             * [LiouvilleLambdaFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LiouvilleLambdaFunctionTest.java)

src/main/java/com/thealgorithms/maths/KrishnamurthyNumber.java

@@ -1,31 +1,38 @@
 package com.thealgorithms.maths;
 
-/* This is a program to check if a number is a Krishnamurthy number or not.
-A number is a Krishnamurthy number if the sum of the factorials of the digits of the number is equal
-to the number itself. For example, 1, 2 and 145 are Krishnamurthy numbers. Krishnamurthy number is
-also referred to as a Strong number.
+/**
+ * Utility class for checking if a number is a Krishnamurthy number.
+ *
+ * A Krishnamurthy number (also known as a Strong number) is a number whose sum of the factorials of its digits is equal to the number itself.
+ *
+ * For example, 145 is a Krishnamurthy number because 1! + 4! + 5! = 1 + 24 + 120 = 145.
+ * <b>Example usage:</b>
+ * <pre>
+ * boolean isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(145);
+ * System.out.println(isKrishnamurthy); // Output: true
+ *
+ * isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(123);
+ * System.out.println(isKrishnamurthy); // Output: false
+ * </pre>
  */
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-
 public final class KrishnamurthyNumber {
+
     private KrishnamurthyNumber() {
     }
 
-    // returns True if the number is a Krishnamurthy number and False if it is not.
-
-    public static boolean isKMurthy(int n) {
-        // initialising the variable s that will store the sum of the factorials of the digits to 0
-        int s = 0;
-        // storing the number n in a temporary variable tmp
+    /**
+     * Checks if a number is a Krishnamurthy number.
+     *
+     * @param n The number to check
+     * @return true if the number is a Krishnamurthy number, false otherwise
+     */
+    public static boolean isKrishnamurthy(int n) {
         int tmp = n;
+        int s = 0;
 
-        // Krishnamurthy numbers are positive
         if (n <= 0) {
             return false;
-        } // checking if the number is a Krishnamurthy number
-        else {
+        } else {
             while (n != 0) {
                 // initialising the variable fact that will store the factorials of the digits
                 int fact = 1;
@@ -43,15 +50,4 @@ public static boolean isKMurthy(int n) {
             return tmp == s;
         }
     }
-
-    public static void main(String[] args) throws IOException {
-        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
-        System.out.println("Enter a number to check if it is a Krishnamurthy number: ");
-        int n = Integer.parseInt(br.readLine());
-        if (isKMurthy(n)) {
-            System.out.println(n + " is a Krishnamurthy number.");
-        } else {
-            System.out.println(n + " is NOT a Krishnamurthy number.");
-        }
-    }
 }

src/test/java/com/thealgorithms/maths/KrishnamurthyNumberTest.java

@@ -0,0 +1,62 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the KrishnamurthyNumber class.
+ */
+public class KrishnamurthyNumberTest {
+
+    /**
+     * Test the isKrishnamurthy method with a known Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthyTrue() {
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(145));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a number that is not a Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthyFalse() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(123));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with zero.
+     */
+    @Test
+    public void testIsKrishnamurthyZero() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(0));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a negative number.
+     */
+    @Test
+    public void testIsKrishnamurthyNegative() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(-145));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a single-digit Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthySingleDigitTrue() {
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(1));
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(2));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a single-digit number that is not a Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthySingleDigitFalse() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(3));
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(4));
+    }
+}