From d80fd0c623306ad14bb76a02328e812e435725d2 Mon Sep 17 00:00:00 2001
From: Alex Klymenko <alexanderklmn@gmail.com>
Date: Sat, 17 Aug 2024 20:35:36 +0200
Subject: [PATCH] refactor: `DecimalToBinary` (#5339)

---
 .../conversions/DecimalToBinary.java          | 84 ++++++++-----------
 .../conversions/DecimalToBinaryTest.java      | 21 +++++
 2 files changed, 56 insertions(+), 49 deletions(-)
 create mode 100644 src/test/java/com/thealgorithms/conversions/DecimalToBinaryTest.java

diff --git a/src/main/java/com/thealgorithms/conversions/DecimalToBinary.java b/src/main/java/com/thealgorithms/conversions/DecimalToBinary.java
index 471724ff9..e8d033e00 100644
--- a/src/main/java/com/thealgorithms/conversions/DecimalToBinary.java
+++ b/src/main/java/com/thealgorithms/conversions/DecimalToBinary.java
@@ -1,63 +1,49 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
- * This class converts a Decimal number to a Binary number
+ * This class provides methods to convert a decimal number to a binary number.
  */
 final class DecimalToBinary {
+    private static final int BINARY_BASE = 2;
+    private static final int DECIMAL_MULTIPLIER = 10;
+
     private DecimalToBinary() {
     }
 
     /**
-     * Main Method
-     *
-     * @param args Command Line Arguments
+     * 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
      */
-    public static void main(String[] args) {
-        conventionalConversion();
-        bitwiseConversion();
-    }
+    public static int convertUsingConventionalAlgorithm(int decimalNumber) {
+        int binaryNumber = 0;
+        int position = 1;
 
-    /**
-     * This method converts a decimal number to a binary number using a
-     * conventional algorithm.
-     */
-    public static void conventionalConversion() {
-        int n;
-        int b = 0;
-        int c = 0;
-        int d;
-        Scanner input = new Scanner(System.in);
-        System.out.printf("Conventional conversion.%n Enter the decimal number: ");
-        n = input.nextInt();
-        while (n != 0) {
-            d = n % 2;
-            b = b + d * (int) Math.pow(10, c++);
-            n /= 2;
-        } // converting decimal to binary
-        System.out.println("\tBinary number: " + b);
-        input.close();
-    }
-
-    /**
-     * This method converts a decimal number to a binary number using a bitwise
-     * algorithm
-     */
-    public static void bitwiseConversion() {
-        int n;
-        int b = 0;
-        int c = 0;
-        int d;
-        Scanner input = new Scanner(System.in);
-        System.out.printf("Bitwise conversion.%n Enter the decimal number: ");
-        n = input.nextInt();
-        while (n != 0) {
-            d = (n & 1);
-            b += d * (int) Math.pow(10, c++);
-            n >>= 1;
+        while (decimalNumber > 0) {
+            int remainder = decimalNumber % BINARY_BASE;
+            binaryNumber += remainder * position;
+            position *= DECIMAL_MULTIPLIER;
+            decimalNumber /= BINARY_BASE;
         }
-        System.out.println("\tBinary number: " + b);
-        input.close();
+
+        return binaryNumber;
+    }
+
+    /**
+     * 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
+     */
+    public static int convertUsingBitwiseAlgorithm(int decimalNumber) {
+        int binaryNumber = 0;
+        int position = 1;
+
+        while (decimalNumber > 0) {
+            int leastSignificantBit = decimalNumber & 1;
+            binaryNumber += leastSignificantBit * position;
+            position *= DECIMAL_MULTIPLIER;
+            decimalNumber >>= 1;
+        }
+        return binaryNumber;
     }
 }
diff --git a/src/test/java/com/thealgorithms/conversions/DecimalToBinaryTest.java b/src/test/java/com/thealgorithms/conversions/DecimalToBinaryTest.java
new file mode 100644
index 000000000..f194951e9
--- /dev/null
+++ b/src/test/java/com/thealgorithms/conversions/DecimalToBinaryTest.java
@@ -0,0 +1,21 @@
+package com.thealgorithms.conversions;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+public class DecimalToBinaryTest {
+
+    @ParameterizedTest
+    @CsvSource({"0, 0", "1, 1", "2, 10", "5, 101", "10, 1010", "15, 1111", "100, 1100100"})
+    void testConvertUsingConventionalAlgorithm(int decimal, int expectedBinary) {
+        assertEquals(expectedBinary, DecimalToBinary.convertUsingConventionalAlgorithm(decimal));
+    }
+
+    @ParameterizedTest
+    @CsvSource({"0, 0", "1, 1", "2, 10", "5, 101", "10, 1010", "15, 1111", "100, 1100100"})
+    void testConvertUsingBitwiseAlgorithm(int decimal, int expectedBinary) {
+        assertEquals(expectedBinary, DecimalToBinary.convertUsingBitwiseAlgorithm(decimal));
+    }
+}