請問父類構建器為啥要用super呢

第一段代碼中，

super()和this的作用分別是什么呢

<?php
echo?"真棒！";

package?com.imooc.newdada;

public?class?Car?{
	public?int?carId;
	public?String?carName;
	public?double?carRental;
	public?Car(int?carId,?String?carName,?double?carRental)?{
		super();
		this.carId?=?carId;
		this.carName?=?carName;
		this.carRental?=?carRental;
	}
}

package?com.imooc.newdada;

public?class?PassengerCar?extends?Car{
	int?carCapacity;
	
	public?PassengerCar(int?carId,?String?carName,?double?carRental,
			int?carCapacity)?{
		super(carId,?carName,?carRental);
		this.carCapacity?=?carCapacity;
	}	

}

package?com.imooc.newdada;

public?class?Truck?extends?Car?{
	int??capForgoods;
	
	public?Truck(int?carId,?String?carName,?double?carRental,?int?capForgoods)?{
		super(carId,?carName,?carRental);
		this.capForgoods?=?capForgoods;
	}
}

package?com.imooc.newdada;

public?class?PickupTruck?extends?Car?{
	int?carCapacity;
	int??capForgoods;
	public?PickupTruck(int?carId,?String?carName,?double?carRental,
			int?carCapacity,?int?capForgoods)?{
		super(carId,?carName,?carRental);
		this.carCapacity?=?carCapacity;
		this.capForgoods?=?capForgoods;
	}

}

package?com.imooc.newdada;

public?class?DadaIndex?{
	public?static?void?main(String[]?args)?{
	System.out.println("ID\t"+"車類型\t"+"租費/天\t"+"可載人數\t"+"可載噸數");
	PassengerCar[]?passengerCar={new?PassengerCar(1,?"奔馳A2",?500,?4)};
	PickupTruck[]?pickupTruck={new?PickupTruck(2,"皮卡",400,2,200)};	
	Truck[]?truck={new?Truck(3,"大眾貨車",800,1000)};
	showCars(passengerCar,?pickupTruck,?truck);
	}
	public?static?void?showCars(PassengerCar[]?passengerCar,PickupTruck[]?pickupTruck,	Truck[]?truck){
		for(int?i=0;i<passengerCar.length;i++){
				System.out.println(passengerCar[i].carId+"\t"+passengerCar[i].carName+"\t"+passengerCar[i].carRental+"\t"+passengerCar[i].carCapacity+"\t"+null);
		}
		for(int?i=0;i<pickupTruck.length;i++){
				System.out.println(pickupTruck[i].carId+"\t"+pickupTruck[i].carName+"\t"+pickupTruck[i].carRental+"\t"+pickupTruck[i].carCapacity+"\t"+pickupTruck[i].capForgoods);
		}
		for(int?i=0;i<truck.length;i++){
				System.out.println(truck[i].carId+"\t"+truck[i].carName+"\t"+truck[i].carRental+"\t"+null+"\t"+truck[i].capForgoods);
		}
	}
}

package?com.imooc.dada;
//父類
public?class?Car?{
	public?int?carId;
	public?String?carName;
	public?double?carRental;
	public?int?carCapacity;
	public?int?capForgoods;
	public?Car(int?carId,?String?carName,?double?carRental,?int?carCapacity)?{
		super();
		this.carId?=?carId;
		this.carName?=?carName;
		this.carRental?=?carRental;
		this.carCapacity?=?carCapacity;
	}
	
	public?Car(int?carId,?String?carName,?double?carRental,?int?carCapacity,
			int?capForgoods)?{
		super();
		this.carId?=?carId;
		this.carName?=?carName;
		this.carRental?=?carRental;
		this.carCapacity?=?carCapacity;
		this.capForgoods?=?capForgoods;
	}
}

package?com.imooc.dada;

public?class?PassengerCar?extends?Car?{

	public?PassengerCar(int?carId,?String?carName,?double?carRental,
			int?carCapacity)?{
		super(carId,?carName,?carRental,?carCapacity);
		//?TODO?Auto-generated?constructor?stub
	}

}

package?com.imooc.dada;

public?class?PickupTruck?extends?Car{

	public?PickupTruck(int?carId,?String?carName,?double?carRental,
			int?carCapacity,?int?capForgoods)?{
		super(carId,?carName,?carRental,?carCapacity,?capForgoods);
		//?TODO?Auto-generated?constructor?stub
	}
	

}

package?com.imooc.dada;

public?class?Truck?extends?Car?{

	public?Truck(int?carId,?String?carName,?double?carRental,?int?carCapacity)?{
		super(carId,?carName,?carRental,?carCapacity);
		//?TODO?Auto-generated?constructor?stub
	}

}

package?com.imooc.dada;

import?java.util.Scanner;

public?class?DadaIndex?{
	
	public?static?void?main(String[]?args)?{
		//?TODO?Auto-generated?method?stub
		Car[]?cars={new?PassengerCar(1,"奧迪A4",500,4),new?PassengerCar(2,"馬自達6",400,4),new?PickupTruck(3,?"皮卡雪5",?500,?2,?253),new?PickupTruck(4,?"皮卡雪6",?1060,?2,?520),new?PassengerCar(5,"奔馳A6",600,4),new?Truck(6,"松花江",400,400)};
		System.out.println("歡迎使用答答租車系統"+"\n"+"您是否要租車:1是???0否");	
		isNeed();
		System.out.println("您可租車的類型及其價目表：");
		carList(cars);
		System.out.println("請輸入您要租車的數量：");
		int?num=getNum();
		int[]?arr=chooseCar(num);
		System.out.println("請輸入租車天數：");
		int?days=getDays();
		System.out.println("您所選的車輛信息及費用如下：");
		System.out.println("ID\t"+"車類型\t"+"租費/天\t"+"可載人數\t"+"可載噸數");
		getCarInfo(arr,cars,days);
	}
	public?static?void?isNeed(){
		Scanner?input=new?Scanner(System.in);
		int?choose=input.nextInt();
		if(choose==1){
			return;
		}else{
			System.exit(0);
		}
	}
	public?static?void?carList(Car[]?cars){	
		System.out.println("ID\t"+"車類型\t"+"租費/天\t"+"可載人數\t"+"可載噸數");
		for(int?i=0;i<cars.length;i++){
			System.out.println(cars[i].carId+"\t"+cars[i].carName+"\t"+cars[i].carRental+"\t"+cars[i].carCapacity+"\t"+cars[i].capForgoods);
				}	
	}
	public?static?int?getNum(){
		Scanner?input1=new?Scanner(System.in);
		int?num=input1.nextInt();
		return?num;
	}
	public?static?int[]?chooseCar(int?num){
		int[]?arr=new?int[num];
		int?i;
		double?sum;
		for(i=0;i<num;i++){
			System.out.println("請選擇第"+(i+1)+"輛車的id：");
			Scanner?input2=new?Scanner(System.in);
			?arr[i]=input2.nextInt();
		}	
		return?arr;
	}
	public?static?int?getDays(){
		Scanner?input1=new?Scanner(System.in);
		int?days=input1.nextInt();
		return?days;
	}
	public?static?void?getCarInfo(int?arr[],Car[]?cars,int?days){
		//用較短的數組的長度作為循環條件
		double?money=0;
		int?peopleNum=0;
		double?weight=0;
		int?i,j;
		for(?i=0;i<arr.length;i++){
			for(?j=0;j<cars.length;j++){
				if(arr[i]==cars[j].carId){
				money=money+cars[j].carRental*days;
				peopleNum=peopleNum+cars[j].carCapacity;
				weight=weight+cars[j].capForgoods;
				System.out.println(cars[j].carId+"\t"+cars[j].carName+"\t"+cars[j].carRental+"\t"+cars[j].carCapacity+"\t"+cars[j].capForgoods);
				}
			}
		}
		System.out.println("總費用："+money+"\t"+"可載總人數："+peopleNum+"\t"+"可載貨物："+weight);
		
	}	
}