convert.java

public static int binaryToDecimal(String binary) {
    int decimal = 0;
    int position = 0;
    for (int x = binary.length() - 1; x >= 0; x--) {
        // Saber si es 1 o 0; primero asumimos que es 1 y abajo comprobamos
        short digit = 1;
        if (binary.charAt(x) == '0') {
            digit = 0;
        }
        double multiplier = Math.pow(2, position);
        decimal += digit * multiplier;
        position++;
    }
    return decimal;
}

public static String decimalToBinary(int decimal) {
    if (decimal <= 0) {
        return "0";
    }
    String binary = "";
    while (decimal > 0) {
        short remainder = (short) (decimal % 2);
        decimal = decimal / 2;
        binary = String.valueOf(remainder) + binary;
    }
    return binary;
}