Java双文件实现计算器时如何将week1.java输入变量传递到Switch.java

问题原因 #

你在week1类的main方法里定义的num1、num2、operator1都是方法局部变量，作用域仅限main方法内部，Switch类没有权限直接访问这些变量，且你调用switchcase()方法时未将变量作为参数传递，所以Switch类无法识别这些变量。

修复方案 #

第一步 修改Switch.java的方法定义 #

给switchcase()方法添加入参，接收运算需要的两个数字和运算符：

public class Switch
{
    // 新增3个入参：第一个操作数、运算符、第二个操作数
    void switchcase(int num1, char operator1, int num2)
    {
        int operator2 = 0; // 运算结果变量移到方法内部定义
        switch(operator1){
            case '+':
                operator2 = num1 + num2;
                System.out.println("Addition: " + num1 + " " + operator1 + " " + num2 + " = " + operator2 );
                break;
            case '-':
                operator2 = num1 - num2;
                System.out.println("Subtraction: " + num1 + " " + operator1 + " " + num2 + " = " + operator2 );
                break;
            case '*':
                operator2 = num1 * num2;
                System.out.println("Multiplication: " + num1 + " " + operator1 + " " + num2 + " = " + operator2 );
                break;
            case '/':
                // 补充除数为0判断，避免运行崩溃
                if(num2 == 0){
                    System.out.println("错误：除数不能为0");
                    return;
                }
                operator2 = num1 / num2;
                System.out.println("Division: " + num1 + " " + operator1 + " " + num2 + " = " + operator2 );
                break;
            // 补充非法运算符处理
            default:
                System.out.println("错误：不支持的运算符");
        }
    }
}

第二步 修改week1.java的方法调用 #

调用switchcase()时将三个变量作为参数传入：

import java.util.Scanner;
public class week1
{
    public static void main(String[] args) {
        int num1;
        int num2;
        Scanner input = new Scanner(System.in);
        
        System.out.print("Input a number:");
        num1 = input.nextInt();
        
        System.out.print("Input a Math :");
        char operator1 = input.next().charAt(0);
        
        System.out.print("Input a number:");
        num2 = input.nextInt();

        Switch swish = new Switch();
        // 传递三个参数到switchcase方法
        swish.switchcase(num1, operator1, num2);
        // 关闭输入流避免资源泄漏
        input.close();
    }
}

内容的提问来源于stack exchange，提问作者Pxyke