Use stack and achieved a binary full adder sum (JAVA)

Use stack and achieved a binary full adder sum (JAVA) (Leetcode 67)

Stack implementation using the reverse order of the input binary string, each using an adder to realize a summation

Core code adder:

s = a ^ b ^ c; //求和结果
c = (a & b) | (a & c) | (b & c); //进位

Topic: Leetcode binary sum

Given two binary string, and return to their (expressed in binary).

Input is non-empty string and contains only numbers 1and 0.

Example 1:

输入: a = "11", b = "1"
输出: "100"

Example 2:

输入: a = "1010", b = "1011"
输出: "10101"

Code:

class Solution {
    public String addBinary(String a, String b) {
        Stack<Boolean> sa = new Stack<>();
        Stack<Boolean> sb = new Stack<>();
        for(char ch : a.toCharArray()) {
            sa.push(ch == '1');
        }
        for(char ch : b.toCharArray()) {
            sb.push(ch == '1');
        }
        Stack<Boolean> ans = new Stack<>();
        boolean ta, tb, s, car = false;
        while(true) {
            if(!sa.isEmpty()) {
                ta = sa.pop();
            }
            else {
                ta = false;
            }
            if(!sb.isEmpty()) {
                tb = sb.pop();
            }
            else {
                tb = false;
            }
            s = ta ^ tb ^ car;
            car = (ta & tb) | (ta & car) | (tb & car);
            ans.push(s);
            if(sa.empty() && sb.empty()) {
                break;
            }
        }
        if(car) {
            ans.push(car);
        }
        StringBuilder res = new StringBuilder();
        while(!ans.empty()) {
            boolean tmp = ans.pop();
            if(tmp) {
                res.append('1');
            }
            else {
                res.append('0');
            }
        }
        return res.toString();
    }
}