四则运算

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Calculator {

    public static void main(String[] args) {
        System.out.println("请输入数字和运算符");
        BufferedReader bufferedReader = new BufferedReader(
                new InputStreamReader(System.in));
        String num = null;
        int sum = 0;
        try {
            num = bufferedReader.readLine();
            while (!num.equals("bye")) {
                for (int i = 0; i < num.length(); i++) {
                    if (Character.toString(num.charAt(i)).equals("+")) {
                        sum = Integer.parseInt(num.substring(0, i))
                                + Integer.parseInt(num.substring(i + 1));
                        break;
                    } else if (Character.toString(num.charAt(i)).equals("-")) {
                        sum = Integer.parseInt(num.substring(0, i))
                                - Integer.parseInt(num.substring(i + 1));
                        break;
                    } else if (Character.toString(num.charAt(i)).equals("*")) {
                        sum = Integer.parseInt(num.substring(0, i))
                                * Integer.parseInt(num.substring(i + 1));
                        break;
                    } else if (Character.toString(num.charAt(i)).equals("/")) {
                        sum = Integer.parseInt(num.substring(0, i))
                                / Integer.parseInt(num.substring(i + 1));
                        break;
                    }
                }
                System.out.println(sum);
                num = bufferedReader.readLine();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}