Question

当我运行代码时，出现错误。奇怪的是，当我将files.getTimeScore();更改为files.getLineScore();时，它会毫无错误地执行。但是，这些功能几乎完全相同。

当我从getTimeScore()类的main中运行FileIO方法时，它运行正常。

错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tetris.FileIO.loadHighscores(FileIO.java:52)
at tetris.FileIO.getTimeScores(FileIO.java:31)
at tetris.HighScores.<init>(HighScores.java:39)
at tetris.Menu$2.actionPerformed(Menu.java:74)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)

代码

高分类

public HighScores(){
    // init A
    super("Highscores");
    c=getContentPane();
    test = new String[100][2];
    files = new FileIO();

    mainPanel = new JPanel();
    test = files.getTimeScores();
    timeTable = new JTable(test,timeTitles );
    test = files.getLineScores();
    lineTable = new JTable(test,lineTitles );

FileIO类

import java.io.File;
import java.io.InputStream;
import java.io.Writer;
import java.util.Scanner;


public class FileIO {
    private File file;
    private Scanner filescScanner, lineScanner;
    private Writer fileWriter, lineWriter;
    private String[][] data;

    public FileIO () {
        data = new String[100][2];
    }

    public String[][] getLineScores(){
        return this.loadHighscores(this.getClass().getResourceAsStream("LineHighscores.txt"));
    }

    public String[][] getTimeScores(){
        return this.loadHighscores(this.getClass().getResourceAsStream("TimeHighscores.txt"));
    }

    public String[][] loadHighscores( InputStream resourceStream){
        int x=0;
        String test = "";

        filescScanner = new Scanner(resourceStream);

        while(filescScanner.hasNextLine()&& x<100) {
            lineScanner = new Scanner(filescScanner.nextLine());
            lineScanner.useDelimiter("-/-");

            data[x][0]=lineScanner.next();//name
            data[x][1]=lineScanner.next();//data
            x++;
        }
        lineScanner.close();
        filescScanner.close();
        return data;
    }

Answer 1

我猜你的lineScanner是null。无法在FileIO中看到您将其初始化的位置。您只能在while子句中初始化它。因此，如果您的文件为空，则在您尝试关闭它时它仍然为空。

Answer 2

对于TimeHighscores.txt文件，

行扫描程序为空。所以这意味着while循环没有被执行 - 甚至没有执行过。

Answer 3

您不测试可以访问的那些文件。即如果resourceStream为空。

使用此方法并不重要，因为如果要添加高分，则无法轻松更新这些文件。

文件I / O上的java.lang.NullPointerException

错误

代码

3 个答案: