怎么用switch语句！！（要融合两个条件）

package com.xxx.test;

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        System.out.println("请输入第一个字符");
        String str1=new Scanner(System.in).nextLine();
        System.out.println("请输入第二个字符");
        String str2=new Scanner(System.in).nextLine();
        switch (str1.toUpperCase()) {
        case "M":
                System.out.println("专业是Mathematics(数学)");
                switch (str2) {
                case "1":
                    System.out.println("年级是大一");
                    break;
                case "2":
                    System.out.println("年级是大二");
                    break;
                case "3":
                    System.out.println("年级是大三");
                    break;
                case "4":
                    System.out.println("年级是大四");
                    break;
                default:
                    break;
                }
            break;
        case "C":
            System.out.println("专业是Computer Science(计算机科学)");
            switch (str2) {
            case "1":
                System.out.println("年级是大一");
                break;
            case "2":
                System.out.println("年级是大二");
                break;
            case "3":
                System.out.println("年级是大三");
                break;
            case "4":
                System.out.println("年级是大四");
                break;
            default:
                break;
            }
            break;
        case "I":
            System.out.println("专业是Information Technology(信息技术)");
            switch (str2) {
            case "1":
                System.out.println("年级是大一");
                break;
            case "2":
                System.out.println("年级是大二");
                break;
            case "3":
                System.out.println("年级是大三");
                break;
            case "4":
                System.out.println("年级是大四");
                break;
            default:
                break;
            }
            break;

        default:
            System.out.println("没有这个东西哦~");
            break;
        }
        
    }
    
}