• 考点：字符串的遍历

class Solution {
    public String replaceSpace(String s) {
        StringBuilder tmp = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == ' ') {
                tmp.append("%20");
            } else {
                tmp.append(s.charAt(i));
            }
        }
        return tmp + "";
    }
}