Update DecimalToBinary.java

Added the JUnit test in this.

Author: Swarali-31

src/main/java/com/thealgorithms/conversions/DecimalToBinary.java

@@ -1,4 +1,5 @@
-package com.thealgorithms.conversions;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
 
 /**
  * This class provides methods to convert a decimal number to a binary number.
@@ -8,10 +9,12 @@ final class DecimalToBinary {
     private static final int DECIMAL_MULTIPLIER = 10;
 
     private DecimalToBinary() {
+        // Prevent instantiation of utility class
     }
 
     /**
      * Converts a decimal number to a binary number using a conventional algorithm.
+     * 
      * @param decimalNumber the decimal number to convert
      * @return the binary representation of the decimal number
      */
@@ -31,6 +34,7 @@ public static int convertUsingConventionalAlgorithm(int decimalNumber) {
 
     /**
      * Converts a decimal number to a binary number using a bitwise algorithm.
+     * 
      * @param decimalNumber the decimal number to convert
      * @return the binary representation of the decimal number
      */
@@ -39,11 +43,38 @@ public static int convertUsingBitwiseAlgorithm(int decimalNumber) {
         int position = 1;
 
         while (decimalNumber > 0) {
-            int leastSignificantBit = decimalNumber & 1;
+            int leastSignificantBit = decimalNumber & 1; // Extract LSB using bitwise AND
             binaryNumber += leastSignificantBit * position;
             position *= DECIMAL_MULTIPLIER;
-            decimalNumber >>= 1;
+            decimalNumber >>= 1; // Right shift the decimal number to move to the next bit
         }
+
         return binaryNumber;
     }
+
+    /**
+     * Unit tests for DecimalToBinary conversions.
+     */
+    public static class DecimalToBinaryTest {
+
+        @Test
+        void testConvertUsingConventionalAlgorithm() {
+            // Testing conversion using conventional method
+            assertEquals(1101, DecimalToBinary.convertUsingConventionalAlgorithm(13)); // 13 in binary is 1101
+            assertEquals(1010, DecimalToBinary.convertUsingConventionalAlgorithm(10)); // 10 in binary is 1010
+            assertEquals(1, DecimalToBinary.convertUsingConventionalAlgorithm(1)); // 1 in binary is 1
+            assertEquals(0, DecimalToBinary.convertUsingConventionalAlgorithm(0)); // 0 in binary is 0
+            assertEquals(10010, DecimalToBinary.convertUsingConventionalAlgorithm(18)); // 18 in binary is 10010
+        }
+
+        @Test
+        void testConvertUsingBitwiseAlgorithm() {
+            // Testing conversion using bitwise method
+            assertEquals(1101, DecimalToBinary.convertUsingBitwiseAlgorithm(13)); // 13 in binary is 1101
+            assertEquals(1010, DecimalToBinary.convertUsingBitwiseAlgorithm(10)); // 10 in binary is 1010
+            assertEquals(1, DecimalToBinary.convertUsingBitwiseAlgorithm(1)); // 1 in binary is 1
+            assertEquals(0, DecimalToBinary.convertUsingBitwiseAlgorithm(0)); // 0 in binary is 0
+            assertEquals(10010, DecimalToBinary.convertUsingBitwiseAlgorithm(18)); // 18 in binary is 10010
+        }
+    }
 }