From e32cab3189a195a25fe5eeb4089d807ec7d2b7d7 Mon Sep 17 00:00:00 2001
From: Alex Klymenko <alexanderklmn@gmail.com>
Date: Fri, 16 Aug 2024 16:48:47 +0200
Subject: [PATCH] refactor: `BinaryToDecimal` (#5330)

---
 .../conversions/BinaryToDecimal.java          | 42 +++++++++----------
 .../conversions/BinaryToDecimalTest.java      |  9 ++++
 2 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/src/main/java/com/thealgorithms/conversions/BinaryToDecimal.java b/src/main/java/com/thealgorithms/conversions/BinaryToDecimal.java
index 67b815ab6..36c0790e5 100644
--- a/src/main/java/com/thealgorithms/conversions/BinaryToDecimal.java
+++ b/src/main/java/com/thealgorithms/conversions/BinaryToDecimal.java
@@ -1,37 +1,33 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
  * This class converts a Binary number to a Decimal number
  */
 final class BinaryToDecimal {
+    private static final int BINARY_BASE = 2;
+
     private BinaryToDecimal() {
     }
 
-    public static long binaryToDecimal(long binNum) {
-        long binCopy;
-        long d;
-        long s = 0;
-        long power = 0;
-        binCopy = binNum;
-        while (binCopy != 0) {
-            d = binCopy % 10;
-            s += d * (long) Math.pow(2, power++);
-            binCopy /= 10;
-        }
-        return s;
-    }
-
     /**
-     * Main Method
+     * Converts a binary number to its decimal equivalent.
      *
-     * @param args Command line arguments
+     * @param binaryNumber The binary number to convert.
+     * @return The decimal equivalent of the binary number.
+     * @throws IllegalArgumentException If the binary number contains digits other than 0 and 1.
      */
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.print("Binary number: ");
-        System.out.println("Decimal equivalent:" + binaryToDecimal(sc.nextLong()));
-        sc.close();
+    public static long binaryToDecimal(long binaryNumber) {
+        long decimalValue = 0;
+        long power = 0;
+
+        while (binaryNumber != 0) {
+            long digit = binaryNumber % 10;
+            if (digit > 1) {
+                throw new IllegalArgumentException("Incorrect binary digit: " + digit);
+            }
+            decimalValue += (long) (digit * Math.pow(BINARY_BASE, power++));
+            binaryNumber /= 10;
+        }
+        return decimalValue;
     }
 }
diff --git a/src/test/java/com/thealgorithms/conversions/BinaryToDecimalTest.java b/src/test/java/com/thealgorithms/conversions/BinaryToDecimalTest.java
index 2471f919a..9045d1002 100644
--- a/src/test/java/com/thealgorithms/conversions/BinaryToDecimalTest.java
+++ b/src/test/java/com/thealgorithms/conversions/BinaryToDecimalTest.java
@@ -1,8 +1,11 @@
 package com.thealgorithms.conversions;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 public class BinaryToDecimalTest {
 
@@ -30,4 +33,10 @@ public class BinaryToDecimalTest {
         assertEquals(262144L, BinaryToDecimal.binaryToDecimal(1000000000000000000L));
         assertEquals(524287L, BinaryToDecimal.binaryToDecimal(1111111111111111111L));
     }
+
+    @ParameterizedTest
+    @CsvSource({"2", "1234", "11112", "101021"})
+    void testNotCorrectBinaryInput(long binaryNumber) {
+        assertThrows(IllegalArgumentException.class, () -> BinaryToDecimal.binaryToDecimal(binaryNumber));
+    }
 }