1class Solution {2    public boolean isValid(String s) {3        Deque<Character> stack = new ArrayDeque<>();4        for (char c : s.toCharArray()) {5            if (c == '(') stack.push(')');6            else if (c == '[') stack.push(']');7            else if (c == '{') stack.push('}');8            else if (stack.isEmpty() || stack.pop() != c) return false;9        }10        return stack.isEmpty();11    }12}