added binary string to decimal converter

Author: TaranjeetSinghKalsi

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

@@ -30,4 +30,34 @@ public static long binaryToDecimal(long binaryNumber) {
         }
         return decimalValue;
     }
+
+    /**
+     * Converts a binary String to its decimal equivalent using bitwise operators.
+     *
+     * @param binary The binary number to convert.
+     * @return The decimal equivalent of the binary number.
+     * @throws IllegalArgumentException If the binary number is null or empty, or contains digits other than 0 and 1.
+     */
+    public static long binaryStringToDecimal(String binary) {
+        if (binary == null || binary.isEmpty()) {
+            throw new IllegalArgumentException("Input cannot be null or empty");
+        }
+
+        boolean isNegative = binary.charAt(0) == '-';
+        if (isNegative) {
+            binary = binary.substring(1);
+        }
+
+        long decimalValue = 0;
+
+        for (char bit : binary.toCharArray()) {
+            if (bit != '0' && bit != '1') {
+                throw new IllegalArgumentException("Incorrect binary digit: " + bit);
+            }
+            // shift left by 1 (multiply by 2) and add bit value
+            decimalValue = (decimalValue << 1) | (bit - '0');
+        }
+
+        return isNegative ? -decimalValue : decimalValue;
+    }
 }

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

@@ -18,25 +18,39 @@ public void testBinaryToDecimal() {
         assertEquals(5, BinaryToDecimal.binaryToDecimal(101));
         assertEquals(63, BinaryToDecimal.binaryToDecimal(111111));
         assertEquals(512, BinaryToDecimal.binaryToDecimal(1000000000));
+
+        assertEquals(0, BinaryToDecimal.binaryStringToDecimal("0"));
+        assertEquals(1, BinaryToDecimal.binaryStringToDecimal("1"));
+        assertEquals(5, BinaryToDecimal.binaryStringToDecimal("101"));
+        assertEquals(63, BinaryToDecimal.binaryStringToDecimal("111111"));
+        assertEquals(512, BinaryToDecimal.binaryStringToDecimal("1000000000"));
     }
 
     @Test
     // Test converting negative binary numbers
     public void testNegativeBinaryToDecimal() {
         assertEquals(-1, BinaryToDecimal.binaryToDecimal(-1));
         assertEquals(-42, BinaryToDecimal.binaryToDecimal(-101010));
+
+        assertEquals(-1, BinaryToDecimal.binaryStringToDecimal("-1"));
+        assertEquals(-42, BinaryToDecimal.binaryStringToDecimal("-101010"));
     }
 
     @Test
     // Test converting binary numbers with large values
     public void testLargeBinaryToDecimal() {
         assertEquals(262144L, BinaryToDecimal.binaryToDecimal(1000000000000000000L));
         assertEquals(524287L, BinaryToDecimal.binaryToDecimal(1111111111111111111L));
+
+        assertEquals(262144L, BinaryToDecimal.binaryStringToDecimal("1000000000000000000"));
+        assertEquals(524287L, BinaryToDecimal.binaryStringToDecimal("1111111111111111111"));
     }
 
     @ParameterizedTest
     @CsvSource({"2", "1234", "11112", "101021"})
     void testNotCorrectBinaryInput(long binaryNumber) {
         assertThrows(IllegalArgumentException.class, () -> BinaryToDecimal.binaryToDecimal(binaryNumber));
+
+        assertThrows(IllegalArgumentException.class, () -> BinaryToDecimal.binaryStringToDecimal(Long.toString(binaryNumber)));
     }
 }