public class AddBinary {

public static String addBinary(String a, String b) {

StringBuilder sBuilder=new StringBuilder();

int i=a.length()-1;

int j=b.length()-1;

int carry=0;

while(i>=0||j>=0) {

int sum=carry;

if(i>=0) sum+=a.charAt(i--)-'0';

if(j>=0) sum+=b.charAt(j--)-'0';

sBuilder.append(sum%2);

carry=sum/2;

}

if(carry!=0) {

sBuilder.append(carry);

}

return sBuilder.reverse().toString();

}

public static void main(String[] args) {

// TODO Auto-generated method stub

String s1="11";

String s2="1";

System.out.println(addBinary(s1, s2));

}

}