public int calPoints(String[] ops) {
    int  sum = 0 ;
    Stack<Integer> valids = new Stack<>();
    for (String c : ops) {
		if(c.matches("-?\\d+"))
		{
			int temp = Integer.parseInt(c);
			sum += temp;
			valids.push(temp);
		}
		else
		{
			if(c == "C" || c == "c")
			{
				sum -= valids.pop();
			}
			else if(c == "D" || c == "d")
			{
				int peek = valids.peek();
				int temp = peek * 2;
				valids.push(temp);
				sum += temp;
			}
			else
			{
				int temp = valids.pop();
				int peek = valids.peek();
				sum += temp + peek;
				valids.push(temp);
			}
		}
	}
    return sum;
}