答答租车系统（使用接口实现）

父类Car

public abstract class Car {
    public String carType;
    public int rentPrice;
}

载人接口

public interface IPassengerCapacity {
    public int getcarrypassenger();
}

载货接口

public interface IGoodsCapacity {
    public int getcarrygoods();
}

载人类

public class passengerCar extends Car implements IPassengerCapacity {
    private int carrypassenger;//载客量
    //构造方法
     passengerCar(String type,int rentprice,int carrypassenger){
        this.carType=type;
        this.rentPrice=rentprice;
        this.carrypassenger=carrypassenger;
    }   
    public int getcarrypassenger() {
        // TODO Auto-generated method stub
        return carrypassenger;
    }

}

卡车类

public class Trunk extends Car implements IGoodsCapacity {
    private int carrygoods;     
    Trunk(String type,int rentprice,int carrygoods){
        this.carType=type;
        this.rentPrice=rentprice;
        this.carrygoods=carrygoods;
    }

    public int getcarrygoods() {
        // TODO Auto-generated method stub
        return carrygoods;
    }
}

皮卡类

public class PickUp extends Car implements IPassengerCapacity, IGoodsCapacity {
    private int carrypassenger;//载客量
    private int carrygoods;
    PickUp(String type,int rentprice,int carrypassenger,int carrygoods){
        this.carType=type;
        this.rentPrice=rentprice;
        this.carrypassenger=carrypassenger;
        this.carrygoods=carrygoods;
    }

    public int getcarrypassenger() {
        // TODO Auto-generated method stub
        return carrypassenger;
    }

    public int getcarrygoods() {
        // TODO Auto-generated method stub
        return carrygoods;
    }
}

主函数

import java.util.Scanner;
public class Initial {  
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Car[] carsforRnet={new passengerCar("奥迪A4",500,4),new passengerCar("马自达6",400,4),new PickUp("皮卡雪6",450,4,2),new passengerCar("金龙",800,20),new Trunk("松花江",400,4),new Trunk("依维柯",1000,20)};     
        System.out.println("欢迎进入答答租车系统：");
        System.out.println("您是否要租车：1：是 0：否");
        Scanner sn=new Scanner(System.in);
        String input=sn.next();
        int num=1;
        if (input.equals("1")) {
            System.out.println("您可租车的类型及其价目表:");
            System.out.println("序号\t汽车名称\t租金\t容量");
            for (Car newcar:carsforRnet){
                if (newcar instanceof passengerCar) {
                    System.out.println(num + ".\t" + newcar.carType + "\t" + newcar.rentPrice + "元/天" + "\t" + "载人："+ ((passengerCar)newcar).getcarrypassenger() + "人"); num++; }
                if (newcar instanceof PickUp) {
                    System.out.println(num + ".\t" + newcar.carType + "\t" + newcar.rentPrice + "元/天" + "\t" + "载人："+ ((PickUp)newcar).getcarrypassenger() + "人"+ "载货："+ ((PickUp)newcar).getcarrygoods() + "吨"); num++; }                              
                if (newcar instanceof Trunk) {
                     System.out.println(num + ".\t" + newcar.carType + "\t" + newcar.rentPrice + "元/天" + "\t" + "载货："+ ((Trunk)newcar).getcarrygoods() + "吨"); num++; }                                 
            }   
            System.out.println("请输入要租汽车的数量:");
            int carNum= sn.nextInt();//使用汽车数量
            if(carNum<0){
                System.out.println("输入有误，请重新输入！");
                System.out.println("请输入要租汽车的数量:");
                carNum= sn.nextInt();//使用汽车数量   
            }           
            int[] carNums = new int[carNum];
            for (int i = 0; i < carNums.length; i++) {
                System.out.println("请输入第"+(i+1)+"辆车的序号");
                carNums[i]=sn.nextInt();
                if((carNums[i]>6)||(carNums[i]<0)){
                    System.out.println("输入有误，请重新输入第"+(i+1)+"辆车的序号");
                    if(i>=0){
                    i--;
                    }
                    else {
                        i=0;
                    }
                    continue;                   
                }               
            }
            System.out.println("请输入用车天数：");
            int useDays=sn.nextInt();
            if(useDays<0){
                System.out.println("输入有误，请重新输入！");
                System.out.println("请输入用车天数：");
                useDays= sn.nextInt();//使用汽车数量
            }
            int Sumcountpeople = 0;
            int Sumcountgoods = 0;
            int rent=0;
            System.out.println("您的账单：\n***可载人的车有:");
            for (int i = 0; i < carNums.length; i++) { 
                if ((carsforRnet[carNums[i] - 1] instanceof passengerCar) || (carsforRnet[carNums[i] - 1] instanceof PickUp)) 
                { 
                    System.out.print(carsforRnet[carNums[i] - 1].carType + "\t"); 
                    if((carsforRnet[carNums[i] - 1] instanceof passengerCar)){
                    Sumcountpeople = Sumcountpeople+((passengerCar)carsforRnet[carNums[i] - 1]).getcarrypassenger(); }
                    if((carsforRnet[carNums[i] - 1] instanceof PickUp)){
                        Sumcountpeople = Sumcountpeople+((PickUp)carsforRnet[carNums[i] - 1]).getcarrypassenger(); }                    
                }                   
        }   
            System.out.println("共可载人：" + Sumcountpeople + "人！");

            System.out.println("***可载货的车有:");
            for (int i = 0; i < carNums.length; i++) { 
                if ((carsforRnet[carNums[i] - 1] instanceof Trunk) || (carsforRnet[carNums[i] - 1] instanceof PickUp)) 
                { 
                    System.out.print(carsforRnet[carNums[i] - 1].carType + "\t"); 
                    if((carsforRnet[carNums[i] - 1] instanceof Trunk)){
                        Sumcountgoods = Sumcountgoods+((Trunk)carsforRnet[carNums[i] - 1]).getcarrygoods(); }
                    if((carsforRnet[carNums[i] - 1] instanceof PickUp)){
                        Sumcountgoods = Sumcountgoods+((PickUp)carsforRnet[carNums[i] - 1]).getcarrygoods(); }                  
                }                   
        }   
            System.out.println("共可载货：" + Sumcountgoods + "吨！");
            for (int i = 0; i < carNums.length; i++) { 
                rent=rent+(carsforRnet[carNums[i] - 1]).rentPrice;
            }
            rent=rent*useDays;
            System.out.println("***租车总价格:" + rent + "元！");

        }
        else {
            System.out.println("感谢使用再见");
        }

    }

}