栈系列一＞删除字符中的所有相邻重复项

class Solution {
    public String removeDuplicates(String _s) {
        StringBuffer ret = new StringBuffer();

        int n = _s.length();
        char[] s = _s.toCharArray();

        for(char x : s){

            if(ret.length() > 0 && x == ret.charAt(ret.length()-1)){
                ret.deleteCharAt(ret.length()-1);
            }else {
                ret.append(x);
            }
        }
        
        return ret.toString();
    }
}