NumberSystems

import java.util.Stack;

public class Program {

    public static void decToBinString(int number) {
        String bin = "";
        while (number != 0) {
            bin += number % 2;
            number /= 2;
        }
        // reverse
        for(int i = bin.length() - 1; i >= 0; i--) {
            System.out.print(bin.charAt(i));
        }
    }

    public static void decToBinStack(int number) {
        Stack<Integer> bin = new Stack<Integer>();
        while (number != 0) {
            bin.push(number % 2);
            number /= 2;
        }

        while (!bin.empty()) {
            System.out.print(bin.pop());
        }
    }

    public static int binToDec(int bin) {
        int dec = 0;
        int power = 0;
        while (bin != 0) {
            dec += (bin % 10) * Math.pow(2, power);
            power++;
            bin /= 10;
        }
        return dec;
    }

    public static void main(String[] args) {
        while (true) {
            System.out.println("1. BIN -> DEC");
            System.out.println("2. DEC -> BIN");
            System.out.println("3. EXIT");
        }

    }
}