https://oj.leetcode.com/problems/valid-parentheses/

Valid Parentheses.java

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

About stack
注意所有Collection类型里面要用Character或者Integer封装为对象。