LeetCode----67. Add Binary(java)

package addBinary67;
/*
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
*/
public class Solution {
public static String addBinary(String a, String b) {
//ensure a.length()<=b.length()
if (a.length()>b.length())
return addBinary(b,a);
char[] chara=a.toCharArray();
char[] charb=b.toCharArray();
int lena=chara.length;
int lenb=charb.length;
StringBuilder sb=new StringBuilder();
int carry=0;
//add the same length numbers
for (int i=0;i<lena;i++){
int inta=chara[lena-1-i]-'0';
int intb=charb[lenb-1-i]-'0';
sb.append(inta^intb^carry);
carry=(inta&intb)|((inta^intb)&carry);
}
//add the longer length numbers
for (int i=lenb-lena-1;i>=0;i--){
int intb=charb[i]-'0';
sb.append(intb^carry);
carry=intb&carry;
}
//judge the first bit
if(carry>0)
sb.append(carry);
return sb.reverse().toString();

}
public static void main(String[] args) {
// TODO Auto-generated method stub
String a="10100000100100110110010000010101111011011001101110111111111101000000101111001110001111100001101";
String b="110101001011101110001111100110001010100001101011101010000011011011001011101111001100000011011110011";
//String a="101";
//String b="10111";
System.out.println(addBinary(a,b));
//110111101100010011000101110110100000011101000101011001000011011000001100011110011010010011000000000

}

}