TCPServerCalculator

package task1;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class TCPServer
{

    public static List<String> function(String input)
    {
        List<String> list = new ArrayList();
        double result = 0;
        List<String> tokens = new ArrayList<>();
        tokens.addAll(Arrays.asList(input.split(":")));
        try
        {
            String operator = tokens.get(0);
            double operand1 = Double.parseDouble(tokens.get(1));
            double operand2 = 0;
            switch (operator)
            {
                case "+":
                    operand2 = Double.parseDouble(tokens.get(2));
                    result = operand1 + operand2;
                    list.add(Double.toString(result));
                    break;
                case "-":
                    operand2 = Double.parseDouble(tokens.get(2));
                    result = operand1 - operand2;
                    list.add(Double.toString(result));
                    break;
                case "*":
                    operand2 = Double.parseDouble(tokens.get(2));
                    result = operand1 * operand2;
                    list.add(Double.toString(result));
                    break;
                case "/":
                    operand2 = Double.parseDouble(tokens.get(2));
                    result = operand1 / operand2;
                    list.add(Double.toString(result));
                    break;
                case "%":
                    operand2 = Double.parseDouble(tokens.get(2));
                    result = operand1 % operand2;
                    list.add(Double.toString(result));
                    break;
                case "sqrt()":
                    if(operand1<0)
                    {
                        list.add("Infinity");
                    }
                    else
                    {
                        result = Math.sqrt(operand1);
                        list.add(Double.toString(result));
                    }
                    break;
                case "sin()":
                    result = Math.sin(operand1);
                    list.add(Double.toString(result));
                    break;
                case "cos()":
                    result = Math.cos(operand1);
                    list.add(Double.toString(result));
                    break;
                default:
                    list.add("Invalid operation");
                    break;
            }
        }
        catch (Exception e)
        {
            list.add(e.toString());
        }
        return list;
    }

    public static void main(String[] args)
    {
        try
        {
            ServerSocket serverSocket = new ServerSocket(1256);
            System.out.println("Waiting for client....");
            Socket connectionSocket = serverSocket.accept();

            BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
            String sentenceFromClient = inFromClient.readLine();

            String modifiedResult = function(sentenceFromClient).get(0);
            DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
            outToClient.writeBytes(modifiedResult + '\n');

            serverSocket.close();

        }
        catch (IOException ex)
        {
            System.out.println("Unable to attach " + ex);
        }
    }
}