public class Test {

    static String check(String input) {
        Stack<Character> stack=new Stack<>();
        for (int pos = 0; pos < input.length(); pos++) {
            char c = input.charAt(pos);
            if (c == '(') {
               stack.push(c);
            }
            if (c == ')') {
                if (stack.empty())  return "false";
                stack.pop();
            }

        }
        if (stack.empty()) {
            return "True";
        } else {
            return "False";
        }
    }

    public static void main(String[] args) {
        System.out.println(check("()()")); // true
        System.out.println(check("(()())")); // true
        System.out.println(check(")("));   // false
        System.out.println(check("(()"));  // false
        System.out.println(check("()("));  // false
        System.out.println(check("((((")); // false
    }

}