leetcode67:Add Binary

package com.leetcode;public class Solution67 { public static  String addBinary(String a, String b) { if( a == null || a.isEmpty() ){ return b; } if( b == null || b.isEmpty() ){ return a; }  char[ ] aArray = a.toCharArray(); char[ ] bArray = b.toCharArray(); StringBuilder std = new StringBuilder();  int i = aArray.length - 1; int j = bArray.length - 1; int flag = 0; while( i > -1 || j> -1 || flag == 1 ){ int  aByte = (i > -1) ? Character.getNumericValue( aArray[ i-- ] ) : 0 ; int  bByte = (j > -1) ? Character.getNumericValue( bArray[ j-- ] ) : 0 ; int result = aByte ^ bByte^ flag; flag =  aByte + bByte + flag >=2 ? 1 : 0 ; std.append(result); }  return std.reverse().toString();    }public static void main(String[] args) {System.out.println(Solution67.addBinary("1", "1"));}}