Removing Stars From a String

1class Solution {
2    // time O(n)
3    // space O(n)
4    public String removeStars(String s) {
5        Stack<Character> stack = new Stack<Character>();
6
7        for (int i = 0; i < s.length(); i++) {
8            char c = s.charAt(i);
9
10            if (c == '*') {
11                if (!stack.isEmpty()) {
12                    stack.pop();
13                }
14            }
15            else {
16                stack.push(c);
17            }
18        }
19
20
21        StringBuilder sb = new StringBuilder(stack.size());
22        sb.setLength(stack.size());
23        for (int i = stack.size() - 1; i >= 0; i--) {
24            sb.setCharAt(i, stack.pop());
25        }
26
27        return sb.toString();
28    }
29}