[LeetCode] Grind 75 questions (2/75) Valid Parentheses

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class Solution {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<>();

        for(int i = 0; i < s.length(); i++) {
            if(s.charAt(i) == '(') {
                stack.push(')');
            } else if (s.charAt(i) =='{') {
                stack.push('}');
            } else if (s.charAt(i) == '[') {
                stack.push(']');
            } else {
                if(stack.isEmpty()) return false;
                char c = stack.pop();
                if(c != s.charAt(i)) return false;
            }
        }
        return stack.isEmpty();
    }
}

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public E push(E item)
public E pop()
public E peek()
public boolean empty()
public int search(Object o)