Valid Parentheses

public class Solution {
public boolean isValid(String s) {
if (s == null || s.length() % 2 == 1) {
return false;
}
Stack<Character> stack = new Stack<>();
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == '(' || s.charAt(i) == '[' || s.charAt(i) == '{') {
stack.push(s.charAt(i));
continue;
}
if (stack.isEmpty()) {
return false;
}
if ((s.charAt(i) == ')' && stack.peek() =='(') || (s.charAt(i) == ']' && stack.peek() =='[') || (s.charAt(i) == '}' && stack.peek() =='{')) {
stack.pop();
} else {
return false;
}
}
if (stack.isEmpty()) {
return true;
} else {
return false;
}
}
}