import java.lang.*; import java.util.*; class Parentheses { public static boolean isValid(String s) { HashMap map = new HashMap(); map.put(')','('); map.put(']','['); map.put('}','{'); Stack stack = new Stack(); char[] arr = s.toCharArray(); stack.push(arr[0]); for (int i = 1; i < arr.length; i++) { if (arr[i] == '(' || arr[i] == '[' || arr[i] == '{') stack.push(arr[i]); else if (map.get(arr[i]) == stack.peek()) stack.pop(); } return stack.isEmpty(); } public static void main(String[] args) { String s = ")("; System.out.println(isValid(s)); } }