写个租车系统不容易，借鉴了别人的

汽车类
public class Car {
int id;
String name;
double money;
int load;
int set;
public Car(int id,String name,double money,int load,int set) {
this.id = id;
this.name = name;
this.money = money;
this.load = load;
this.set = set;
}

}
新类继承汽车类
public class TwoCar extends Car{

public TwoCar(int id, String name, double money, int load, int set) {
    super(id, name, money, load, set);

}
public String toString() {
    return id+"\t" +name+"\t" + money+"\t" +load+"\t" + set;

}

}
测试类

import java.util.Scanner;

public class Test {
public static void main(String[] args) {

    int sumSet=0;
    int sumLoad = 0;
    int sumMoney = 0;
    int pay=0;
    String canSet = "";
    String canLoad = "";

    Car [] cars = new Car[5];
    cars[0] = new TwoCar(1, "奇瑞", 200, 0, 4);
    cars[1] = new TwoCar(2, "大奔", 500, 0, 4);
    cars[2] = new TwoCar(3, "皮卡", 300, 2, 4);
    cars[3] = new TwoCar(4, "江淮", 300, 5, 0);
    cars[4] = new TwoCar(5, "解放", 500, 10, 0);

    System.out.println("欢迎使用租车系统"+"\n"+"输入任意数字继续，输入0退出。请输入");
    Scanner in = new Scanner(System.in);

    if(in.nextInt()==0) {
        System.out.println("感谢您的使用");
    }else {
        System.out.println("目前可以选择的车型有：");
        System.out.println("序号"+"\t"+"车型"+"\t"+"金额/天"+"\t"+"载重"+"\t"+"座位");
        for(Car c:cars) {
            System.out.println(c);
        }

        System.out.println("请选择您需要租借车辆的数量(请输入0~5之间的整数)");
        int sum = in.nextInt();
        for(int i=0;i<sum;i++) {
            System.out.println("请输入第"+(i+1)+"辆车的序号");
            int id = in.nextInt();
            System.out.println("请输入第"+(i+1)+"辆车的租用时间");
            int day = in.nextInt();
            sumMoney = (int) (day*cars[id-1].money);
            sumSet += cars[id-1].set;
            sumLoad += cars[id-1].load;
            pay += sumMoney;
            if(cars[id-1].set!=0) {
                canSet+=cars[id-1].name+"";
            }
            if(cars[id-1].load!=0) {
                canLoad+=cars[id-1].name+"";
            }
        }
        System.out.println("可载客车型有："+canSet);
        System.out.println("您选择的车型载客量为："+sumSet);
        System.out.println("可载货车型有："+canLoad);
        System.out.println("您选择的车型载货量为："+sumLoad);
        System.out.println("您共需要支付的费用为"+pay+"元");

    }

}

}