20. Valid Parentheses

class Solution {
    public boolean isValid(String s) {
       Stack<Character> stack = new Stack<>();
        
        
        for (char c : s.toCharArray()) {
            
            if (c == '(' || c == '{' || c == '[') {
                stack.push(c);
            }
            
            else if (c == ')' || c == '}' || c == ']') {
                
                if (stack.isEmpty() || !isMatchingPair(stack.pop(), c)) {
                    return false;
                }
            }
        }
        
        
        return stack.isEmpty();
        
    }
     private static boolean isMatchingPair(char open, char close) {
        return (open == '(' && close == ')') ||
               (open == '{' && close == '}') ||
               (open == '[' && close == ']');
    }
}