第七章综合练习空指针异常问题

Question

package gamed;import java.util.ArrayList;import java.util.Collections;import java.util.List;import java.util.Random;import java.util.Scanner;import java.util.concurrent.SynchronousQueue;public class poker {    private String col;    private String num;    List<poker> a = new ArrayList<poker>();    List<player> playertocreate = new ArrayList<player>();        public poker(String col,String num){    this.col=col;    this.num=num;    }        public poker() {        // TODO Auto-generated constructor stub    }    public String getCol() {        return col;    }    public void setCol(String col) {        this.col = col;    }    public String getNum() {        return num;    }    public void setNum(String num) {        this.num = num;    }        public void creat(){        String[] col1 ={"黑桃","红桃","梅花","方片"};        String[] num1 ={"2","3","4","5","6","7","8","9","10","J","Q","K","A"};    for(int i=0;i<col1.length;i++){        for(int j=0;j<num1.length;j++){            poker b = new poker(col1[i],num1[j]);            a.add(b);        }            }    System.out.println("扑克创建完成");    System.out.println("您创建的扑克如下");    for (poker po : a) {        System.out.println(po.col+po.num);        }    }                public void flash(){        Collections.shuffle(a);        System.out.println("洗牌完成");        }                public void  Creatplayer(){        //List<player> playertocreate = new ArrayList<player>();        int i=0;        Scanner console = new Scanner(System.in);        while(i<2){                //try{                System.out.println("请输入第"+(i+1)+"个玩家的姓名");                player player = new player();                console = new Scanner(System.in);                player.setName(console.next());                console = new Scanner(System.in);                try{                System.out.println("请输入第"+(i+1)+"个玩家的ID");                player.setID(console.nextInt());                playertocreate.add(player);                i++;                }catch (Exception e) {                System.out.println("请输入正确的玩家ID");                }                        }        for (player pl : playertocreate) {            System.out.println("欢迎"+pl.getName()+"您的ID为"+pl.getID());        }                }                       public void sendpoker(){        for (player player : playertocreate) {            System.out.println(player.getName()+"拿牌");            Random random = new Random();            for(int i=0;i<2;i++){                player.playerpoker.add(i, (poker)a.get(random.nextInt(a.size())));                System.out.println(player.getName()+"拿到的"+(i+1)                        +"牌为"+(poker)player.playerpoker.get(i));            }        }            }public void match(){        }    public static void main(String[] args) {    poker p = new poker();    p.creat();    p.flash();    p.Creatplayer();    p.sendpoker();}    }加黑部分运行的时候为什么会抛一个空指针异常没太想明白