How can a calculator be implemented in Java to perform addition, subtraction, multiplication, and division?

Here is a simple example code in Java for a calculator that performs addition, subtraction, multiplication, and division.

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("请输入第一个数字：");
        double num1 = scanner.nextDouble();

        System.out.print("请输入运算符(+、-、*、/)：");
        String operator = scanner.next();

        System.out.print("请输入第二个数字：");
        double num2 = scanner.nextDouble();

        double result = 0;

        switch (operator) {
            case "+":
                result = num1 + num2;
                break;
            case "-":
                result = num1 - num2;
                break;
            case "*":
                result = num1 * num2;
                break;
            case "/":
                if (num2 != 0) {
                    result = num1 / num2;
                } else {
                    System.out.println("除数不能为0");
                    return;
                }
                break;
            default:
                System.out.println("不支持的运算符");
                return;
        }

        System.out.println("计算结果：" + result);
    }
}

After running the above code, the program will prompt the user to input two numbers and an operator (+, -, *, /), and then perform the corresponding calculation based on the operator, and output the result.

Please note that the above code is just a simple example with no input validation and exception handling, only capable of performing basic arithmetic operations. In real-world applications, it may be necessary to implement stricter input validation and handle various possible exceptions.