Code007 -- determine whether the string in parentheses matches

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

/**
 *  Given one only includes  '(',')','{','}','[',']' String  s , Determines whether the string is valid .
 *  Valid string needs to meet ：
 *
 *  Opening parentheses must be closed with closing parentheses of the same type .
 *  The left parenthesis must be closed in the correct order .
 *
 *  Example  1：
 *  Input ：s = "()"
 *  Output ：true
 *  Example 2：
 *  Input ：s = "()[]{}"
 *  Output ：true
 *
 *  Example 3：
 *  Input ：s = "(]"
 *  Output ：false
 *
 *  Example 4：
 *  Input ：s = "([)]"
 *  Output ：false
 *
 *  Example 5：
 *  Input ：s = "{[]}"
 *  Output ：true
 *
 *  Tips ：
 * 1 <= s.length <= 104
 * s  Brackets only  '()[]{}'  form 
 *
 */
public class test07 {
    public static void main(String[] args) throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        String s = bf.readLine();

        //System.out.println(s.length());
        System.out.println(s+" Whether it works ："+isValid(s));

    }

//    public static boolean isValid(String s){
//        boolean flag = false;
//        for( int i=(s.length()/2)-1; i >= 0; i--){
//            int j = 1;
//            if ( s.charAt(i) == '(' && s.charAt(i+j) == ')'){
//                flag = true;
//                j += 2;
//            }else if (s.charAt(i) == '[' && s.charAt(i+j) == ']'){
//                flag = true;
//                j += 2;
//            }else if (s.charAt(i) == '{' && s.charAt(i+j) == '}'){
//                flag = true;
//                j += 2;
//            }else{
//                flag = false;
//                break;
//            }
//        }
//        return flag;
//    }
    public static boolean isValid(String s){
        int n = s.length();
        if( n%2 ==1){
            return false;
        }
        Map<Character,Character> map = new HashMap<Character,Character>();
        map.put(')', '(');
        map.put(']', '[');
        map.put('}', '{');
        // Judge with the characteristics of stack first in and last out , The current symbol only needs to match the top element of the stack ： matching , Stack top element out of stack ; conversely , The current element is put on the stack 
        Deque<Character> stack = new LinkedList<Character>();
        for( int i=0; i<n; i++){
            char ch = s.charAt(i);
            if(map.containsKey(ch)){
                if(stack.isEmpty() || stack.peek() != map.get(ch)){ // Determine whether the stack is empty or the top element of the stack does not match the current element 
                    return false;
                }
                stack.pop();  // Stack top element out of stack 
            }else{
                stack.push(ch);  // There is no current element in the stack , The current element is put on the stack （ To put it bluntly '(','[' and '{' These three symbols are stacked ）
            }
        }
        return stack.isEmpty();
    }
}