def calPoints(operations):
    """
    Calculates the total score of a baseball game.
 
    Args:
        operations: A list of strings representing the operations.
 
    Returns:
        The total score after applying all operations.
    """
    stack = []  # Initialize an empty stack to store scores
 
    for op in operations:
        if op.isdigit() or (op.startswith('-') and op[1:].isdigit()): #check if it's an integer
            stack.append(int(op)) # Push integer onto the stack
        elif op == '+':
            if len(stack) >= 2:  # Check for sufficient elements
                stack.append(stack[-1] + stack[-2]) # Add top two elements and push result
            else:
                raise ValueError("Not enough elements in the stack for '+' operation.")
        elif op == 'D':
            if stack:  #Check if stack is not empty
                stack.append(stack[-1] * 2) # Double the top element and push result
            else:
                raise ValueError("Stack is empty. Cannot perform 'D' operation.")
        elif op == 'C':
            if stack:  # Check for elements to pop
                stack.pop() #remove the last element
            else:
                raise ValueError("Stack is empty. Cannot perform 'C' operation.")
        else:
            raise ValueError("Invalid operation: " + op) #Handle Invalid operations
 
 
    return sum(stack) #return the sum of all remaining elements in stack
 

import java.util.Stack;
 
class Solution {
    public int calPoints(String[] operations) {
        Stack<Integer> stack = new Stack<>();
 
        for (String op : operations) {
            if (op.matches("-?\\d+")) { // Check if it's an integer (positive or negative)
                stack.push(Integer.parseInt(op));
            } else if (op.equals("+")) {
                if (stack.size() >= 2) {
                    int second = stack.pop();
                    int first = stack.peek();
                    stack.push(second);
                    stack.push(first + second);
                } else {
                    throw new IllegalArgumentException("Not enough elements for '+'");
                }
            } else if (op.equals("D")) {
                if (!stack.isEmpty()) {
                    stack.push(stack.peek() * 2);
                } else {
                    throw new IllegalArgumentException("Stack is empty for 'D'");
                }
            } else if (op.equals("C")) {
                if (!stack.isEmpty()) {
                    stack.pop();
                } else {
                    throw new IllegalArgumentException("Stack is empty for 'C'");
                }
            } else {
                throw new IllegalArgumentException("Invalid operation: " + op);
            }
        }
 
        int totalScore = 0;
        for (int score : stack) {
            totalScore += score;
        }
        return totalScore;
    }
}