public boolean isValid(String s) {

if(s.length() % 2 == 1) {

return false;

}

Stack<Character> stack = new Stack<Character>();

for(int i = 0; i < s.length(); i++) {

if(s.charAt(i) == '(' || s.charAt(i) == '[' || s.charAt(i) == '{') {

stack.push(s.charAt(i));

} else if(s.charAt(i) == ')' && !stack.isEmpty() && stack.peek() == ')') {

stack.pop();

} else if(s.charAt(i) == ']' && !stack.isEmpty() && stack.peek() == ']') {

stack.pop();

} else if(s.charAt(i) == '}' && !stack.isEmpty() && stack.peek() == '}') {

stack.pop();

} else {

return false;

}

}

return stack.isEmpty();

}