public class Exercise_07 { public static void main(String[] args) { System. out. println(bin2Dec("1100100")); // Purposely throwing an exception... System. out. println(bin2Dec("lafkja")); } public static int bin2Dec(String binary) throws NumberFormatException { if (!isBinary(binary)) { throw new NumberFormatException(binary + " is not a binary number."); } int power = 0; int decimal = 0; for (int i = binary. length() - 1; i >= 0; i--) { if (binary. charAt(i) == '1') { decimal += Math. pow(2, power); } power++; } return decimal; } public static boolean isBinary(String binary) { for (char ch : binary. toCharArray()) { if (ch != '1' && ch != '0') return false; } return true; } }