Question

所以我试图将存储在一个类Liquor的ArrayList中的数据显示到另一个类Bar中。 ArrayList保存5个字符串（酒的名称）和5个整数（每种酒的量）。当我运行代码来显示信息时，我得到一个很长的错误：

线程“AWT-EventQueue-0”中的异常java.lang.NullPointerException at barinventory.BarInv.jButtonDisplayActionPerformed（BarInv.java:355） at barinventory.BarInv.access $ 200（BarInv.java:8）at barinventory.BarInv $ 3.actionPerformed（BarInv.java:219）at javax.swing.AbstractButton.fireActionPerformed（AbstractButton.java:2022）在 javax.swing.AbstractButton中的$ Handler.actionPerformed（AbstractButton.java:2348）在 javax.swing.DefaultButtonModel.fireActionPerformed（DefaultButtonModel.java:402）在 javax.swing.DefaultButtonModel.setPressed（DefaultButtonModel.java:259）在 javax.swing.plaf.basic.BasicButtonListener.mouseReleased（BasicButtonListener.java:252）在java.awt.Component.processMouseEvent（Component.java：6535）at javax.swing.JComponent.processMouseEvent（JComponent.java:3324）at java.awt.Component.processEvent（Component.java:6300）at java.awt.Container.processEvent（Container.java:2236）at java.awt.Component.dispatchEventImpl（Component.java:4891）at java.awt.Container.dispatchEventImpl（Container.java:2294）at java.awt.Component.dispatchEvent（Component.java:4713）at java.awt.LightweightDispatcher.retargetMouseEvent（Container.java:4888）在 java.awt.LightweightDispatcher.processMouseEvent（Container.java:4525） at java.awt.LightweightDispatcher.dispatchEvent（Container.java:4466）在java.awt.Container.dispatchEventImpl（Container.java:2280）at java.awt.Window.dispatchEventImpl（Window.java:2750）at java.awt.Component.dispatchEvent（Component.java:4713）at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:758）at at java.awt.EventQueue.access $ 500（EventQueue.java:97）at java.awt.EventQueue $ 3.run（EventQueue.java:709）at java.awt.EventQueue $ 3.run（EventQueue.java:703）at java.security.AccessController.doPrivileged（Native Method）at java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）在 java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:86）在java.awt.EventQueue $ 4.run（EventQueue.java:731）at java.awt.EventQueue $ 4.run（EventQueue.java:729）at java.security.AccessController.doPrivileged（Native Method）at java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）在java.awt.EventQueue.dispatchEvent（EventQueue.java:728）at java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:201）在 java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:116）在 java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:101）在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:93） at java.awt.EventDispatchThread.run（EventDispatchThread.java:82） BUILD STOPPED（总时间：12秒）

我的酒类：

final class Liquor
{
    //String[] liquor = {"Vodka", "Whiskey", "Rum", "Gin", "Brandy"};
    private final String vodka, whiskey, rum, gin, brandy;
    private final int vCount, wCount, rCount, gCount, bCount;
    ArrayList<Liquor> liquors = new ArrayList<>();

//    public Liquor(ArrayList<Liquor> liquors)
//    {
//        
//        this.vodka = "Vodka";
//        this.whiskey = "Whiskey";
//        this.rum = "Rum";
//        this.gin = "Gin";
//        this.brandy = "Brandy";
//        this.vCount = getVC();
//        this.wCount = getWC();
//        this.rCount = getRC();
//        this.gCount = getGC();
//        this.bCount = getBC();
//    } was trying to pass it through the ArrayList itself... Didn't work.
      //The stock number kept being read in as 0.



    public Liquor(String vodka, String whiskey, String rum, String gin, 
            String brandy, int v, int w, int r, int g, int b)
    {
        this.vodka = vodka;
        this.whiskey = whiskey;
        this.rum = rum;
        this.gin = gin;
        this.brandy = brandy;
        this.vCount = v;
        this.wCount = w;
        this.rCount = r;
        this.gCount = g;
        this.bCount = b;
    }

    public String getV()
    {
        return vodka;
    }

    public String getW()
    {
        return whiskey;
    }

    public String getR()
    {
        return rum;
    }

    public String getG()
    {
        return gin;
    }

    public String getB()
    {
        return brandy;
    }

    public int getVC()
    {
        return vCount;
    }

    public int getWC()
    {
        return wCount;
    }

    public int getRC()
    {
        return rCount;
    }

    public int getGC()
    {
        return gCount;
    }

    public int getBC()
    {
        return bCount;
    }

    @Override
    public String toString()
    {
        return "\nLiquor currently in stock:\n" + vodka + ": " + vCount + "\n" +
                whiskey + ": " + wCount + "\n" + rum + ": " + rCount + "\n" +
                gin + ": " + gCount + "\n" + brandy + ": " + bCount;
    }
}

我的酒吧课程：

class Bar
{
    private final String barLoc, barName;
    private final boolean music, food;
    //ArrayList<Liquor> liquor;

    public Bar(String l, String n, boolean m, boolean f)
    {
        this.barLoc = l;
        this.barName = n;
        this.music = m;
        this.food = f;
    }

    //ArrayList<Liquor> liquor = new ArrayList<>();
    private Liquor liquor;

    public Liquor getLiquor()
    {
        return liquor;
    }

    @Override
    public String toString()
    {
        return "The " + barLoc + " bar is named: " + barName + "\nLive music: " 
                + music + "\nFood Service: " + food;
    } 
}

用于显示的代码：

for(int i=0; i<bars.size(); i++)
        {
            jTextAreaDisplay.append(jTextAreaDisplay.getText() 
                    + bars.get(i).toString() + bars.get(i).getLiquor().toString() 
                    + "\n\n");

        }

我认为这个问题与初始化我的Bar类中的private Liquor liquor;有关，我已经尝试过不同的方法。但是地图册无法做到正确。任何帮助将不胜感激！

示例运行：

（barLocation）栏名为：（barName）

现场音乐:(真或假）

食品服务:(真或假）

现有的白酒：
     伏特加:(库存量）

威士忌:(库存量）

朗姆酒:(库存量）
     杜松子酒:(库存量）

白兰地:(库存量）

Answer 1

据我所见，你从来没有初始化酒。

初始化看起来像这样

Liquor liquor = new Liquor("data", "data", ...);

我没有达到创造一个含有更多液体（伏特加等）的单一酒对象的目的。但也许你有理由。如果没有，那么我会设计不同的酒，因为你所做的并不像现实。通常情况下，酒类应该具有这样的属性：

public String name;
public double alcohol;

然后我会在你的栏中创建一个Liquors的ArrayList并用一些值填充它。

ArrayList<Liquor> liquors = new ArrayList<Liquor>();
//Fill with something like 4 liquors i call them vodka 0, 1, 2 and 3 and fill them with the alcohol value of 40
for(int i = 0; i < 4; i++){
  liquors.add(new Liquor("Wodka"+i, 40));
}

现在我的fill方法显然要求你的Liquid类有一个带2个参数的构造函数（String name，int alcohol）

Answer 2

您尚未初始化Liquor对象。请尝试以下语句

private Liquor liquor=new Liquor("vodka",""...,1,2,..);

将数组从一个类中的ArrayList获取到另一个类

2 个答案: