Binary_decimal.java

import javax.swing.JOptionPane;

public class Binary_decimal {
    public static void main(String args[]) {
        String binaryStr = JOptionPane.showInputDialog(null,
                "Enter a binary number to transform it into a decimal number:",
                "Conversion of binary numbers", JOptionPane.PLAIN_MESSAGE);
        while (binaryStr.contains("1") == false && binaryStr.contains("0") == false) {
            JOptionPane.showMessageDialog(null, "Please, enter a binary number.",
                    "Error", JOptionPane.WARNING_MESSAGE);
            binaryStr = JOptionPane.showInputDialog(null,
                "Enter a binary number to transform it into a decimal number:",
                "Conversion of binary numbers", JOptionPane.PLAIN_MESSAGE);
        }
        int len = binaryStr.length();
        int result = 0;
        for (int i = len - 1; i >= 0; i--) {
            char digit = binaryStr.charAt(i);
            int digitValue = Character.getNumericValue(digit);
            result += digitValue * Math.pow(2, len - 1 - i);
        }
        JOptionPane.showMessageDialog(null, "The binary number in decimal is: " + result, "Result",
                JOptionPane.PLAIN_MESSAGE);
    }
}