Question

我有一个名为Player的类，它定义了Player的特性。我在另一个类中有一个名为readPlayer的方法：

void readPlayer(String playerInfo) {
    int j = 0;
    int playerNumber = 0;
    int playerCount = 0;
    String splitPipe = "\\|"; // split by pipe
    String splitColon = "\\:"; // split by colon
    String splitInput[] = playerInfo.split(splitPipe + "|" + splitColon);
    for (int i = 0; i < splitInput.length; i += 5) {
        playerCount++; // keeps track of how many players there are
    }
    players = new Player[playerCount];// initializes array to amount of players
    while (playerNumber < playerCount) {
        players[playerNumber] = new Player(Integer.parseInt(splitInput[j]), splitInput[j + 1], splitInput[j + 2],
                splitInput[j + 3], splitInput[j + 4]);
        j += 5;
        playerNumber++;
    }
    pR.printPlayers(players); //ERROR: NullPointerException thrown here
}

但是当我尝试将player数组传递给另一个类的printPlayers时，它会给我和NullPointerException错误

错误详情：

Exception in thread "main" java.lang.NullPointerException
    at ca.bcit.comp2613.PlayerReader.readPlayer(PlayerReader.java:30)
    at ca.bcit.comp2613.Lab2.main(Lab2.java:16)

这是我的主要方法：

static PlayerReader p = new PlayerReader(); 
public static void main(String[] args) {
    if(args.length == 0) { 
        System.out.println("Usage java -jar project.jar <input String>");
        System.exit(-1);
    } else { 
        p.readPlayer(args[0]);
    }
}
}

这是我的printPlayer方法 - 没有什么特别的，现在不做任何事情

public class PlayerReport {

    public void printPlayers(Player players[]) {

    }
}

Answer 1

    public class Player {
    public Player(int parseInt, String string, String string2, String string3,
            String string4) {
        // Do initialization
    }

    public static void main(String args[]) {
        // if(args.length == 0) {
        // System.out.println("Usage java -jar project.jar <input String>");
        // System.exit(-1);
        // } else {
        // p.readPlayer(args[0]);
        // }
        PlayerReader p = new PlayerReader();
        p.readPlayer("playerInfo");
    }
}

class PlayerReport {

    public void printPlayers(Player players[]) {
        System.out.println("Printing....");
    }
}

class PlayerReader {

    void readPlayer(String playerInfo) {
        int j = 0;
        int playerNumber = 0;
        int playerCount = 0;
        String splitPipe = "\\|"; // split by pipe
        String splitColon = "\\:"; // split by colon
        String splitInput[] = playerInfo.split(splitPipe + "|" + splitColon);
        for (int i = 0; i < splitInput.length; i += 5) {
            playerCount++; // keeps track of how many players there are
        }
        Player[] players = new Player[playerCount];// initializes array to
                                                    // amount of players
        while (playerNumber < playerCount) {
            // players[playerNumber] = new
            // Player(Integer.parseInt(splitInput[j]),
            // splitInput[j + 1], splitInput[j + 2], splitInput[j + 3],
            // splitInput[j + 4]);
            players[playerNumber] = new Player(1, "3", "4", "5", "6");

            j += 5;
            playerNumber++;
        }
        PlayerReport pR = new PlayerReport();
        pR.printPlayers(players); // ERROR: NullPointerException thrown here
    }
}

Answer 2

在另一个答案中提到，你没有展示你如何实例化“pR”或“玩家”对象。

不确定“pR”对象是什么，但这是导致Null指针的原因。

将数组传递给java中的另一个方法

2 个答案: