Java HashMap問題中的Zuul Remake

Question

我正在使用BlueJ在Java中完成一部分課程。 我們需要為基於文本的游戲Zuul添加新功能。 我決定開始研究庫存和物料系統。 我在尋找最好的方法時遇到了麻煩，所以我只管了一下。 這是我的代碼。 抱歉，我還沒有發表評論。 游戲可以編譯，但是運行游戲時控制台出現異常。

錯誤：

java.lang.NullPointerException
    at Game.createPlayer(Game.java:15)
    at Game.<init>(Game.java:7)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at bluej.runtime.ExecServer$3.run(ExecServer.java:740)

游戲類（與Java中的Main類等效，這是運行游戲的來源）：

import java.util.*;

public class Game
{
    public Game()
    {
        createPlayer();
        createItems();
    }

    private Entity localPlayer;

    public void createPlayer(){
        Player localPlayer = new Player("Player Name", 0, 0, 0, 0, 0);
        localPlayer.equipArmour("Helm", armourDB.get("Helm")); // This is where I think I have gone wrong
    }

    // Create global hashmap variables
    private HashMap<String, Weapon> weaponsDB;
    private HashMap<String, Armour> armourDB;
    private HashMap<String, Supplement> supplementDB;

    public void createItems(){
        // Create weapons
        weaponsDB = new HashMap<String, Weapon>();

        Weapon weaponFists = new Weapon("Fists", "Weapon", 0, 0, 0, 0, 0, "Melee");
        Weapon weaponSword = new Weapon("Sword", "Weapon", 0, 0, 0, 0, 0, "Melee");
        Weapon weaponBow = new Weapon("Bow", "Weapon", 0, 0, 0, 0, 0, "Ranged");
        Weapon weaponDagger = new Weapon("Dagger", "Weapon", 0, 0, 0, 0, 0, "Melee");

        weaponsDB.put("Fists", weaponFists);
        weaponsDB.put("Sword", weaponSword);
        weaponsDB.put("Bow", weaponBow);
        weaponsDB.put("Dagger", weaponDagger);

        // Create armour
        armourDB = new HashMap<String, Armour>();

        Armour armourBreastplate = new Armour("Breatplate", "Chest", 0, 0, 0, 0, 0);
        Armour armourHelm = new Armour("Helm", "Head", 0, 0, 0, 0, 0);

        armourDB.put("Breastplate", armourBreastplate);
        armourDB.put("Helm", armourHelm);

        // Create supplements
        supplementDB = new HashMap<String, Supplement>();

        Supplement supplementHealthPotion = new Supplement("Health Potion", 0, 0);
        Supplement supplementPowerPotion = new Supplement("Power Potion", 0, 0);

        supplementDB.put("Health Potion", supplementHealthPotion);
        supplementDB.put("Power Potion", supplementPowerPotion);
    }
}

實體類（玩家類和敵人類的構造）：

import java.util.*;

public class Entity
{
    private boolean entityStatus;

    private String entityName;
    private int entityHealth;
    private int entityPower;
    private int entityHealthRegen;
    private int entityPowerRegen;
    private int entityAttackPower;

    private HashMap<String, Armour> entityEquipment;
    private ArrayList<Item> entityInventory;    

    public Entity(
        String paramEntityName,
        int paramEntityHealth,
        int paramEntityPower,
        int paramEntityHealthRegen,
        int paramEntityPowerRegen,
        int paramEntityAttackPower)
    {
        entityStatus = true;

        entityName = paramEntityName;
        entityHealth = paramEntityHealth;
        entityPower = paramEntityPower;
        entityHealthRegen = paramEntityHealthRegen;
        entityPowerRegen = paramEntityPowerRegen;
        entityAttackPower = paramEntityAttackPower;

        entityEquipment = new HashMap<String, Armour>(); // Set all possible equipment slots to null on initial run
        entityEquipment.put("Head", null);
        entityEquipment.put("Shoulders", null);
        entityEquipment.put("Chest", null);
        entityEquipment.put("Hands", null);
        entityEquipment.put("Legs", null);
        entityEquipment.put("Feet", null);
        entityEquipment.put("Weapon", null);

        entityInventory = new ArrayList<Item>();
    }

    public boolean getEntityStatus(){
        return entityStatus;
    }

    public String getEntityName(){
        return entityName;
    }

    public int getEntityHealth(){
        return entityHealth;
    }

    public int getEntityPower(){
        return entityPower;
    }

    public int getEntityHealthRegen(){
        return entityHealthRegen;
    }

    public int getEntityPowerRegen(){
        return entityPowerRegen;
    }

    public int getEntityAttackPower(){
        return entityAttackPower;
    }

    // Equips the player with an item into the equipment slot
    public void equipArmour(String paramEquipmentSlot, Armour paramArmourName){
        entityEquipment.put(paramEquipmentSlot, paramArmourName);
    }

    public void printInventory(){
        System.out.println("Something");
    }
}

我認為主要的問題是我無法全神貫注地使用井號，我需要看一個實時示例以了解其工作原理。 有人可以幫忙嗎？ 如果您還需要我提供其他任何信息，請告訴我。

Answer 1

好吧，這就是問題所在：

armourDB.get("Helm")

此時您尚未初始化armourDB 。 如果在createPlayer() createItems()之前調用createItems() ，則對於該特定行應該沒問題。 但是您仍然不會初始化名為localPlayer的istance變量。 您將只為createPlayer聲明的局部變量賦值。

坦白說，您目前還不清楚要達到的目標，但這是前兩個問題...