[LeetCode]67 Add Binary

public class Solution {
public String addBinary(String a, String b) {

StringBuilder sb = new StringBuilder();

char[] charsA = a.toCharArray();
char[] charsB = b.toCharArray();

int indexA = charsA.length - 1;
int indexB = charsB.length - 1;
boolean carry = false;
while (indexA >= 0 || indexB >= 0)
{
int v = indexA >= 0 ? charsA[indexA] - '0' : 0;
v += indexB >= 0 ? charsB[indexB] - '0' : 0;
if (carry)
v ++;

carry = v > 1;
sb.append(v % 2);

indexA --;
indexB --;
}

if (carry)
sb.append("1");

return sb.reverse().toString();
}
}