백준 17413번 단어 뒤집기 2 [ Java ]

17413번: 단어 뒤집기 2

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException {
        Stack<Character> stack = new Stack<>();
        StringBuilder sb = new StringBuilder();
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        boolean open_tag = false;
        char str[] = br.readLine().toCharArray();
        for (char ch : str) {
            if (ch == '<') {
                open_tag = true;
                while (!stack.isEmpty())
                    sb.append(stack.pop());
                sb.append(ch);
            } else if (ch == ' ') {
                while (!stack.isEmpty())
                    sb.append(stack.pop());
                sb.append(ch);
            } else if (ch == '>') {
                open_tag = false;
                sb.append('>');
            } else if (open_tag) {
                sb.append(ch);
            } else {
                stack.push(ch);
            }
        }
        while (!stack.isEmpty())
            sb.append(stack.pop());
        System.out.print(sb);
    }
}