在Test里可载人的地方出现空指针异常运行不下去，求指点，怎么改呢

package com.caosheng.TEST1;

/*

 * 所有汽车的父类

 * 

 */

public class Car {

private int carNum;//定义汽车的序号

private String carName;//定义汽车的名字

private int carRentMoney;//定义汽车的租金

public int getCarNum() {

return carNum;

}

public void setCarNum(int carNum) {

this.carNum = carNum;

}

public String getCarName() {

return carName;

}

public void setCarName(String carName) {

this.carName = carName;

}

public int getCarRentMoney() {

return carRentMoney;

}

public void setCarRentMoney(int carRentMoney) {

this.carRentMoney = carRentMoney;

}

}

package com.caosheng.TEST1;

/*

 * 定义载客的客车

 * 

 */

public class ZaikeCar extends Car {

private int zaikeNum;//定义载客客车的载客量

public ZaikeCar(int carNum,String carName,int carRentMoney,int zaikeNum){

this.setCarName(carName);

this.setCarNum(carNum);

this.setCarRentMoney(carRentMoney);

this.zaikeNum=zaikeNum;

}

public int getZaikeNum() {

return zaikeNum;

}

public void setZaikeNum(int zaikeNum) {

this.zaikeNum = zaikeNum;

}

}

package com.caosheng.TEST1;

/*

 * 定义一个可以载货也可以载货的皮卡

 */

public class PikaCar extends Car {

private int zaikeNum;//定义皮卡的载客量

private int zaihuoNum;//定义皮卡的载货量

public PikaCar(int carNum,String carName,int carRentMoney,int zaikeNum,int zaihuoNum){

this.setCarNum(carNum);

this.setCarName(carName);

this.setCarRentMoney(carRentMoney);

this.zaikeNum=zaikeNum;

this.zaihuoNum=zaihuoNum;

}

public int getZaikeNum() {

return zaikeNum;

}

public void setZaikeNum(int zaikeNum) {

this.zaikeNum = zaikeNum;

}

public int getZaihuoNum() {

return zaihuoNum;

}

public void setZaihuoNum(int zaihuoNum) {

this.zaihuoNum = zaihuoNum;

}

}

package com.caosheng.TEST1;

/*

 * 构造用于载货的货车

 */

public class ZaihuoCar extends Car {

private int zaihuoNum;//定义货车的载货量

public ZaihuoCar(int carNum,String carName,int carRentMoney,int zaihuoNum){

this.setCarNum(carNum);

this.setCarName(carName);

this.setCarRentMoney(carRentMoney);

this.zaihuoNum=zaihuoNum;

}

public int getZaihuoNum() {

return zaihuoNum;

}

public void setZaihuoNum(int zaihuoNum) {

this.zaihuoNum = zaihuoNum;

}

}

package com.caosheng.TEST1;

import java.util.Scanner;

public class Test {

public static void main(String[] args) {

// TODO Auto-generated method stub

System.out.println("欢迎使用答答租车系统！");

System.out.println("您是否要租车？：1是  0否");

Scanner c = new Scanner(System.in);

int k=c.nextInt();

if(k==1){

System.out.println("您可租车的类型及价格表");

Car [ ] carForRent={new ZaikeCar(1,"奥迪A4",500,4),new ZaikeCar(2,"马自达6",400,4),

                    new PikaCar(3,"皮卡雪6",450,4,2),new ZaikeCar(4," 金龙 ",800,20),

                    new ZaihuoCar(5,"松花江",400,4),new ZaihuoCar(6,"依维柯",1000,20)};

System.out.println("序号"+"\t"+"汽车名称"+"\t"+"租金"+"\t"+"\t"+"容量");

for (Car car : carForRent){

if(car instanceof ZaikeCar){

System.out.println(car.getCarNum()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()

                             +"/天"+"\t"+"载人:"+((ZaikeCar)car).getZaikeNum()+"人");

}

if(car instanceof PikaCar){

System.out.println(car.getCarNum()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()

                             +"/天"+"\t"+

"载人:"+((PikaCar)car).getZaikeNum()+"人"+"\t"+

                             "载货:"+((PikaCar)car).getZaihuoNum()+"吨");

}

if(car instanceof ZaihuoCar){

System.out.println(car.getCarNum()+"\t"+car.getCarName()+"\t"+car.getCarRentMoney()

                             +"/天"+"\t"+"\t"+"载货:"+((ZaihuoCar)car).getZaihuoNum()+"吨");

}

}

System.out.println("请输入您要租车的数量:");

int carNum2=c.nextInt(); //用于接收汽车的总数量

int sumR=0;

int sumM=0;

int [] nameN=new int[carNum2];

for(int i=1;i<=carNum2;i++){

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

int xuhao=c.nextInt();

nameN[i-1]=xuhao;

if(xuhao==1||xuhao==2||xuhao==4){

sumR+=((ZaikeCar)carForRent[i-1]).getZaikeNum();

}else if(xuhao==3){

sumR+=((PikaCar)carForRent[i-1]).getZaikeNum();

sumM+=((PikaCar)carForRent[i-1]).getZaihuoNum();

}else if(xuhao==5||xuhao==6){

sumM+=((ZaihuoCar)carForRent[i-1]).getZaihuoNum();

}else{

System.out.println("您输入的序号有错误");

}

}

//System.out.println(sumR);

System.out.println("请输入您要租车的天数:");

int day=c.nextInt();

System.out.println("您的账单：");

System.out.println("**可载人的车有：");

for(int a:nameN){

System.out.println(a);

}

for(int ii=1;ii<=nameN.length;ii++){

int n=nameN[ii];

if(ii==carForRent[n].getCarNum()){

System.out.print(carForRent[n].getCarName()+"\t");

}

}

System.out.println("共载人"+sumR);

System.out.println("**可载货的车有：");

for(int jj=1;jj<=nameN.length;jj++){

if(jj==carForRent[nameN[jj]].getCarNum()){

System.out.print(carForRent[nameN[jj]].getCarName()+"\t");

}

}

System.out.print("共载货"+sumM);

}else if(k==0){

System.out.println("感谢您的使用再见！");

}else{

System.out.println("您输入的信息有错！");

}

}

}