做得不是很好，没用到接口

//main方法

package com.yesijie;

import java.util.Scanner;

public class Mainprogram {

public static void main(String[] args) {

// TODO Auto-generated method stub

           Welcome welcome=new Welcome();

           welcome.welPrint();

           welcome.choose();

           Salooncar jianianhua=new Salooncar();

           jianianhua.setPassengerNum(5);

           jianianhua.setName("嘉年华");

           jianianhua.setInventory(12);

           jianianhua.setPrice(120);

           jianianhua.setCargoWeight(0);

           Salooncar leikesasi=new Salooncar();

           leikesasi.setPassengerNum(4);

           leikesasi.setName("雷克萨斯");

           leikesasi.setInventory(5);

           leikesasi.setPrice(270);

           leikesasi.setCargoWeight(0);

           Truck jinbei=new Truck();

           jinbei.setCargoWeight(10);

           jinbei.setName("金杯");

           jinbei.setInventory(12);

           jinbei.setPrice(90);

           jinbei.setPassengerNum(0);

           Truck lishi=new Truck();

           lishi.setCargoWeight(15);

           lishi.setName("力狮");

           lishi.setInventory(3);

           lishi.setPrice(110);

           lishi.setPassengerNum(0);

           Picard daoqi=new Picard();

           daoqi.setPassengerNum(4);

           daoqi.setCargoWeight(5);

           daoqi.setName("道奇");

           daoqi.setInventory(4);

           daoqi.setPrice(240);

           Cars cars=new Cars();

           Cars []carType={jianianhua,leikesasi,jinbei,lishi,daoqi};

           System.out.println("序号      车型      载客量/载货量     库存     租金");

           for(int i=0;i<carType.length;i++){//output the information

               if(carType[i].getCargoWeight()==0){

                System.out.println((i+1)+"     "+carType[i].getName()+"         "+

                                       carType[i].getPassengerNum()+"人        "+

                           carType[i].getInventory()+"     "+

                                       carType[i].getPrice());

               }//end if

               else if(carType[i].getPassengerNum()==0){

                System.out.println((i+1)+"     "+carType[i].getName()+"         "+

                           carType[i].getCargoWeight()+"吨        "+

               carType[i].getInventory()+"     "+

                           carType[i].getPrice());

               }//end else if

               else {

                System.out.println((i+1)+"     "+carType[i].getName()+"         "+

                           carType[i].getPassengerNum()+"人"+carType[i].getCargoWeight()

                           +"吨       "+

               carType[i].getInventory()+"     "+

                           carType[i].getPrice());

               }//end else

           }//end for

    int carsNumber1;

    int totalPeople=0;

    int totalWeight=0;

    int totalMoney=0;

    Scanner input=new Scanner(System.in);

    System.out.print("请输入您需要的车辆数量：");

    int carNumber=input.nextInt(); //number of cars customer needs

    for(int i=0;i<carNumber;i++){//输出租车各项信息

    System.out.println("请输入第"+(i+1)+"俩车的序号：");

    carsNumber1=input.nextInt();

    System.out.println("请输入需要租借的天数：");

        int days=input.nextInt();

        totalPeople+=carType[carsNumber1-1].getPassengerNum();

        totalWeight+=carType[carsNumber1-1].getCargoWeight();

        totalMoney+=carType[carsNumber1-1].getPrice()*days;

    }//end for

System.out.println();

    System.out.println("您的租车信息为：");

    for(int i=0;i<carNumber;i++){

    System.out.print(carType[carNumber1[i]].getName()+carDays[i]+"天      ");

    }//end for

    System.out.println();

    System.out.println("您的总载人数为"+totalPeople+"人");

    System.out.println("您的总载货量为"+totalWeight+"吨");

    System.out.println("您的总租金为"+totalMoney+"元");

    System.out.println("Thanks for choosing us!");

}//end main()

}

//car类

package com.yesijie;

public class Cars {

private int passengerNum;

private int cargoWeight;

private int price;

private int inventory;

private String name;

public void setPassengerNum(int passengerNum){

this.passengerNum=passengerNum;

    }

public int getPassengerNum(){

return passengerNum;

}

public void setCargoWeight(int cargoWeight){

this.cargoWeight=cargoWeight;

    }

public int getCargoWeight(){

return cargoWeight;

    }

public void setPrice(int price){

this.price=price;

    }

public int getPrice(){

return price;

    }

public void setInventory(int inventory){

this.inventory=inventory;

    }

public int getInventory(){

return inventory;

    }

public void setName(String name){

this.name=name;

    }

public String getName(){

return name;

    }

}

//皮卡子类

package com.yesijie;

public class Picard extends Cars {

}

//轿车子类

package com.yesijie;

public class Salooncar extends Cars {

}

//货车子类

package com.yesijie;

public class Truck extends Cars {

}

//欢迎界面

package com.yesijie;

import java.util.Scanner;

public class Welcome {

public void welPrint(){

System.out.println("欢迎使用达达租车系统！");

System.out.println("请输入数字选择：1.进入系统   2.离开系统");

}

    public void choose(){

    Scanner input=new Scanner(System.in);

    int i=input.nextInt();//输入的数字

    if(i==1){

    System.out.print("请输入姓名：");

    String name=input.next();

    System.out.print("请输入您的性别：1.男士    2.女士");

    int sex=input.nextInt();

    if(sex==1){

    System.out.println("欢迎"+name+"先生"+"使用达达租车系统");

    }

    else if(sex==2){

    System.out.println("欢迎"+name+"女士"+"使用达达租车系统");

    }

    else {

    System.out.println("请输入正确的性别！");

    welPrint();

    choose();    

    }// end else

    }// end if

    else if(i==2){

    System.out.println("再见！");

    }

    else{

    System.out.println("请输入正确的数字：");

    welPrint();

    choose();

    }//end else

    }//end choose

}//end class Welcome