做了很久，总算做出来了，初学者，感觉代码很多，变量也设了很多，希望有大佬提出好的建议，以下贴出代码

//抽象类
public abstract class Car {
    int num;
    String name;
    int rent;
    int capacity;
    int capacity2;
}
//载人的车类
      public  void SetAll(int Vnum,String Vname,int Vrent,int Vcapacity){
          num=Vnum;
          name=Vname;
          capacity=Vcapacity;
          rent=Vrent;
    }

      public  void PrintAll(){
          System.out.println(num+".\t\t"+name+"\t\t"+rent+"元/天\t\t载人："+capacity+"人");
      }
}
//载货车类
public  class Coach extends Car {
    public  void SetAll(int Cnum,String Cname,int Crent,int Ccapacity){
        num=Cnum;
        name=Cname;
        capacity=Ccapacity;
        rent=Crent;
    }

    public  void PrintAll(){
        System.out.println(num+".\t\t"+name+"\t\t"+rent+"元/天\t\t载货："+capacity+"吨");
    }
}
//能载人也能载货类
public class Pika extends Car{

    public  void SetAll(int Pnum,String Pname,int Prent,int Pcapacity1,int Pcapacity2){
        num=Pnum;
        name=Pname;
        capacity=Pcapacity1;
        capacity2=Pcapacity2;
        rent=Prent;
    }

    public  void PrintAll(){
        System.out.println(num+".\t\t"+name+"\t\t"+rent+"元/天\t\t载人："+capacity+"人"+" 载货："+capacity2+"吨");
    }
}
//main函数
import java.util.Scanner;

public class Dada {
    public static void main(String[] args){
        System.out.println("欢迎使用哒哒租车系统:");
        System.out.println("您是否要租车：1.是 0.否");
        Scanner scan=new Scanner(System.in);
        int k=scan.nextInt();//获取控制台上用户输入的数字
        if(k==1){
            System.out.println("您可租车的类型及价目表：");
            System.out.println("序号\t\t汽车名称\t\t租金\t\t容量");
            Car Aodi=new Van();//创建并显示可租车的对象
            ((Van) Aodi).SetAll(1,"奥迪A4",500,4);
            ((Van) Aodi).PrintAll();
            Car Mazida=new Van();
            ((Van) Mazida).SetAll(2,"马自达6",400,4);
            ((Van) Mazida).PrintAll();
            Car Xue=new Pika();
            ((Pika) Xue).SetAll(3,"皮卡雪6",450,4,2);
            ((Pika) Xue).PrintAll();
            Car Jin=new Van();
            ((Van) Jin).SetAll(4,"金龙",800,20);
            ((Van) Jin).PrintAll();
            Car Song=new Coach();
            ((Coach) Song).SetAll(5,"松花江",400,4);
            ((Coach) Song).PrintAll();
            Car Yi=new Coach();
            ((Coach) Yi).SetAll(6,"依维柯",1000,20);
            ((Coach) Yi).PrintAll();
            System.out.println("请输入您要租汽车的数量：");
            int i=scan.nextInt();
            int Choose,sum=0,rent1=0,CarDate,manned=0,shipment=0,Allsum=0,Allmanned=0,Allshipment=0;//分别为用户选择的车型，单次金额,租车单价,租车天数，载人量，载货量和总金额
            for(int j=1;j<=i;j++){
                System.out.println("请选择您要租的第"+j+"辆车的序号");
                Choose=scan.nextInt();
                if (Choose<1||Choose>6)  System.out.println("请输入正确的序号：");
                else {
                    switch (Choose) {
                        case 1:
                            rent1 = Aodi.rent;
                            manned = Aodi.capacity;
                            shipment = 0;
                            break;
                        case 2:
                            rent1 = Mazida.rent;
                            manned = Mazida.capacity;
                            shipment = 0;
                            break;
                        case 3:
                            rent1 = Xue.rent;
                            manned = Xue.capacity;
                            shipment = Xue.capacity2;
                            break;
                        case 4:
                            rent1 = Jin.rent;
                            manned = Jin.capacity;
                            shipment = 0;
                            break;
                        case 5:
                            rent1 = Song.rent;
                            manned = 0;
                            shipment = Song.capacity;
                            break;
                        case 6:
                            rent1 = Yi.rent;
                            manned = 0;
                            shipment = Yi.capacity;
                            break;
                    }
                    Allmanned+=manned;
                    Allshipment+=shipment;
                    System.out.println("请输入租的天数：");
                    CarDate=scan.nextInt();
                    sum=rent1*CarDate;
                    Allsum+=sum;
                    System.out.println("当前载人数量为"+Allmanned+"个,载货数量为"+Allshipment+"吨");
                    System.out.println("您需要付的金额为："+Allsum);
                }


            }


        }else{
            System.out.println("Bye");
            System.exit(0);
        }
    }
//主要觉得冗长的就是main函数部分，原本想把显示可租车辆和选择车辆写成方法来使用，结果发现在另一个方法中创建的对象在main函数中无法使用，也没想到解决的方法，希望有大佬帮忙！