Valid Parentheses in Java

static boolean isValid(String expression) {
        Stack<Character> myStack = new Stack<>();
        HashMap<Character, Character> myMap = new HashMap<>();

        myMap.put('(', ')');
        myMap.put('{', '}');
        myMap.put('[', ']');

        for (char c : expression.toCharArray())
        {
            if (myMap.containsKey(c))
            {
                myStack.push(myMap.get(c));
            }
            else if (myMap.containsValue(c))
            {
                if (myStack.empty() || myStack.pop() != c)
                {
                    return false;
                }
            }
        }
        return (myStack.empty());
    }