java - Board 线程 "main"java.lang.NullPointerException 中出现异常。 at(Board.java :23) at PiratesDriver. main(PiratesDriver.java:14)

Question

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已关闭 10 年前。

您好，我收到此错误消息，我需要帮助

Exception in thread "main" java.lang.NullPointerException
at Board.<init>(Board.java:23)
at PiratesDriver.main(PiratesDriver.java:14)

我的代码是

import java.util.Scanner;
import java.util.Random;
public class Board {
private final int SIZE=30;
private final int NUM_PLAYERS=2;
**private int diffLevel;**
private Player[] players= new Player[NUM_PLAYERS];
private char[] hurdles=new char[SIZE];

public Board() {
    System.out.println("|||||||||||||||||||||||||||||||||||||||||||||"+"\n||||||||||||||||||||START||||||||||||||||||||\n"+"|||||||||||||||||||||||||||||||||||||||||||||" );
    System.out.print("Enter Diffculty Level for the Game (0=easy, 1=50/50 i.e. not too easy, not too hard, 2=HARD):");
    **SetDifficulty();**
    System.out.println("");
    players[0].SetName(GetPlayerName(0));
    System.out.println("");
    players[1].SetName(GetPlayerName(1));
    DisplayPlayerDetails();
    System.out.println("");
    System.out.println("<<<--GAME BOARD LEGEND-->>>");
    System.out.println("e = This cell contains an easy enemy pirate.");
    System.out.println("t = This cell contains a treasure island.");
    System.out.println("a = This cell contains an abandoned ship.");
    System.out.println("m = This cell contains a mystery island.");
    System.out.println("j = This cell contains a magic chamber.");
    System.out.println(",P = This cell has a player in it.");
    System.out.println("<<<------- ----- ------->>> ");
    System.out.println("");
    SetHurdles();
    DisplayBoard();
}

**void SetDifficulty(){
    Scanner scan= new Scanner(System.in);

    boolean invalid = true;
    diffLevel= scan.nextInt();
    while (!((diffLevel <=2) && (diffLevel>=0))){
        System.out.println("Error, please enter a valid value");
         diffLevel= scan.nextInt();**


    }

}
public String GetPlayerName(int index){
    Scanner scan= new Scanner(System.in);
    System.out.print("Enter Player "+(index+1)+"'s Name: ");
    String playername= scan.nextLine();
    System.out.println(playername+" has no Voodoo doll.");
    System.out.println(playername+" does not have a Ship.");
    return playername;
}
public void DisplayPlayerDetails(){
    System.out.println("------------- PLAYER DETAILS -------------");
    for (int i=0;i<players.length;i++){
        System.out.println("-->Player "+(i+1)+"<--");
        System.out.println("Name: "+players[i].GetName());
        System.out.println("Health: "+players[i].GetHealth()+" potions");
        System.out.println("Treasure: "+players[i].GetWealth()+" gold coins");
        System.out.println("Weapon: "+players[i].WeaponName(players[i].GetWeapon()));
        System.out.println("Voodoo Doll: "+players[i].GetVoodoo());
        System.out.println("Ship: "+players[i].GetShip());
        System.out.println("Position: "+(players[i].GetPosition()+1));
        System.out.println("     ------><------");
    }
    System.out.println("---------------------------------------------");

}
public void SetHurdles(){
    Random randNumGenerator = new Random();
    boolean bool=true;
    int rand;
    int e,h,t,a,m,j;
    if (diffLevel==0){
        e=12;
        h=0;
        }
    else if (diffLevel==1){
        e=6;
        h=6;
    }
    else {
        h=12;
        e=0;
    }
    t=6;
    a=6;
    m=3;
    j=3;
    for (int i=0;i<hurdles.length;i++){

        while(bool){
            rand=randNumGenerator.nextInt(6);
            if (rand==0&& e!=0){
                hurdles[i]='e';
                e--;
                bool=false;
            }
            else if (rand==1&& h!=0){
                hurdles[i]='h';
                h--;
                bool=false;
            }
            else if (rand==2&& t!=0){
                hurdles[i]='t';
                t--;
                bool=false;
            }
            else if (rand==3&& a!=0){
                hurdles[i]='a';
                a--;
                bool=false;
            }
            else if (rand==4&& m!=0){
                hurdles[i]='m';
                m--;
                bool=false;
            }
            else if (rand==5&& j!=0){
                hurdles[i]='j';
                j--;
                bool=false;
            }
            bool=true;
        }
    }

    }
    public void DisplayBoard(){
        System.out.println("---------------------------------------------");
        System.out.println("********PIRATES OF 125 GAME BOARD********");
        for (int i=0;i<5;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
                System.out.print((i+1)+":   "+hurdles[i]);
        }
        System.out.println("");
        for (int i=5;i<10;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
            System.out.print((i+1)+":   "+hurdles[i]);
        }
        System.out.println("");
        for (int i=10;i<15;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
            System.out.print((i+1)+":  "+hurdles[i]);
        }
        System.out.println("");
        for (int i=15;i<20;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
            System.out.print((i+1)+":  "+hurdles[i]);
        }
        System.out.println("");
        for (int i=20;i<25;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
            System.out.print((i+1)+":  "+hurdles[i]);
        }
        System.out.println("");
        for (int i=25;i<30;i++){
            if ((players[0].GetPosition()==i)||(players[1].GetPosition()==i))
                System.out.print((i+1)+":   "+hurdles[i]+"P");
             else 
            System.out.print((i+1)+":  "+hurdles[i]);
        }
        System.out.println("");
        System.out.println("---------------------------------------------");
    }
    public void Play(){
        Board game=new Board();
        for (int i=0; i<players.length;i++){
            DisplayPlayerDetails();
            while(players[i].GetPosition()<hurdles.length){

            players[i].Move();
            if (hurdles[players[i].GetPosition()]=='e'){
                EasyPirate e= new EasyPirate();

            }
            }

        }       
    }
}

我的主要驱动器是

public class PiratesDriver {

     public static void main(String[] args) {
Board piratesOf125 = new Board(); //Instantiate a new board
piratesOf125.Play(); //Play the game 

 }
}

我已经尝试了一个多小时了，我知道问题出在我的 diffLevel 为空或其他什么地方，但我似乎无法修复它，我猜我必须在 SetDifficulty 中修复它() 因为这就是 diffLevel 定义的地方。请需要帮助。哦，第 14 行是 private int diffLevel;

Answer 1

写

players[0] = new Player();
players[1] = new Player(); 

开始然后使用它。请记住:当您创建数组的新实例时，您将在单元格中使用 null(默认)值创建它。在使用它之前，您必须创建对象的实例。

另请参阅:

• Creating an array of objects in Java .
• Arrays of Objects