When two binary strings are added, then the sum returned is also a binary string.

gfg.java

public class gfg {
	static String add_Binary(String x, String y)
	{
		String res = "";

		int d = 0;

		int k = x.length() - 1, l = y.length() - 1;
		while (k >= 0 || l >= 0 || d == 1) {
			d += ((k >= 0) ? x.charAt(k) - '0' : 0);
			d += ((l >= 0) ? y.charAt(l) - '0' : 0);

			res = (char)(d % 2 + '0') + res;
			
			d /= 2;

			k--;
			l--;
		}
		return res;
	}

	public static void main(String[] args) {
		String x = "011011", y = "1010111";
		System.out.println(add_Binary(x,y));
	}
}