if if else else 多选的理解

package com.fqs.test;

import java.util.Scanner;

public class hello {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.print("请在键盘输入1到100间的儿子成绩");

        int my_num=sc.nextInt();//键盘接收输入的值放到my_num中
        if(my_num<=0||my_num>100){
            System.out.print("不合法");
        }
        else if(my_num<80){
            System.out.print("打一顿");
        }
        else if(my_num<90&&my_num>=80){
            System.out.print("变形金刚");
        }
        else if(my_num<100&&my_num>=90){
            System.out.print("游乐场一日游");
        }
        else{
            System.out.print("自行车一辆");
        }
    }
}