refactor: Enhance docs, add more tests in OctalToBinary

Author: Hardvan

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

@@ -1,14 +1,41 @@
 package com.thealgorithms.conversions;
 
 /**
- * Converts any Octal Number to a Binary Number
+ * A utility class to convert an octal (base-8) number into its binary (base-2) representation.
+ *
+ * <p>This class provides methods to:
+ * <ul>
+ *     <li>Convert an octal number to its binary equivalent</li>
+ *     <li>Convert individual octal digits to binary</li>
+ * </ul>
+ *
+ * <h2>Octal to Binary Conversion:</h2>
+ * <p>An octal number is converted to binary by converting each octal digit to its 3-bit binary equivalent.
+ * The result is a long representing the full binary equivalent of the octal number.</p>
+ *
+ * <h2>Example Usage</h2>
+ * <pre>
+ *   long binary = OctalToBinary.convertOctalToBinary(52);
+ *   // Output: 101010 (52 in octal is 101010 in binary)
+ * </pre>
  *
  * @author Bama Charan Chhandogi
+ * @see <a href="https://en.wikipedia.org/wiki/Octal">Octal Number System</a>
+ * @see <a href="https://en.wikipedia.org/wiki/Binary_number">Binary Number System</a>
  */
-
 public final class OctalToBinary {
     private OctalToBinary() {
     }
+
+    /**
+     * Converts an octal number to its binary representation.
+     *
+     * <p>Each octal digit is individually converted to its 3-bit binary equivalent, and the binary
+     * digits are concatenated to form the final binary number.</p>
+     *
+     * @param octalNumber the octal number to convert (non-negative integer)
+     * @return the binary equivalent as a long
+     */
     public static long convertOctalToBinary(int octalNumber) {
         long binaryNumber = 0;
         int digitPosition = 1;
@@ -26,6 +53,19 @@ public static long convertOctalToBinary(int octalNumber) {
         return binaryNumber;
     }
 
+    /**
+     * Converts a single octal digit (0-7) to its binary equivalent.
+     *
+     * <p>For example:
+     * <ul>
+     *     <li>Octal digit 7 is converted to binary 111</li>
+     *     <li>Octal digit 3 is converted to binary 011</li>
+     * </ul>
+     * </p>
+     *
+     * @param octalDigit a single octal digit (0-7)
+     * @return the binary equivalent as a long
+     */
     public static long convertOctalDigitToBinary(int octalDigit) {
         long binaryDigit = 0;
         int binaryMultiplier = 1;

src/test/java/com/thealgorithms/conversions/OctalToBinaryTest.java

@@ -12,4 +12,24 @@ public void testConvertOctalToBinary() {
         assertEquals(101010, OctalToBinary.convertOctalToBinary(52));
         assertEquals(110, OctalToBinary.convertOctalToBinary(6));
     }
+
+    @Test
+    public void testConvertOctalToBinarySingleDigit() {
+        assertEquals(0, OctalToBinary.convertOctalToBinary(0));
+        assertEquals(1, OctalToBinary.convertOctalToBinary(1));
+        assertEquals(111, OctalToBinary.convertOctalToBinary(7));
+    }
+
+    @Test
+    public void testConvertOctalToBinaryMultipleDigits() {
+        assertEquals(100110111, OctalToBinary.convertOctalToBinary(467));
+        assertEquals(111101, OctalToBinary.convertOctalToBinary(75));
+        assertEquals(111100101, OctalToBinary.convertOctalToBinary(745));
+    }
+
+    @Test
+    public void testConvertOctalToBinaryWithZeroPadding() {
+        assertEquals(100001010, OctalToBinary.convertOctalToBinary(412));
+        assertEquals(101101110, OctalToBinary.convertOctalToBinary(556));
+    }
 }