refactor: BinaryToDecimal (#5330)

Author: alxkm

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 BinaryToDecimal() {
-    }
+    private static final int BINARY_BASE = 2;
 
-    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;
+    private BinaryToDecimal() {
     }
 
     /**
-     * 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;
     }
 }

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 void testLargeBinaryToDecimal() {
         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));
+    }
 }