valid parentheses

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