java - 线程 "AWT-EventQueue-0"结果集中出现 java.lang.NullPointerException 异常

Question

我正在尝试运行此代码以将 ResultSet 逐行放入数组中，以便我可以将它们放入 jTable 中。我不明白为什么会出现此错误，我是新手。如果您能帮助我，我将非常感激。

    try {
         int pos = 1;
         for (int r=0;r<rsCount;r++){

             String[] na = null;
             res.absolute(pos);
             int a=1;

             while(res.next()){

                    na[a]=res.getString(a+1);
                    a+=1;

                }

                pos+=1;

                 for(int c=0;c<8;c++){

                         tabla.setValueAt(na[c], r, c);

                 }
         }
    } catch (SQLException ex) {
        Logger.getLogger(Reporte.class.getName()).log(Level.SEVERE, null, ex);
    }
}                              

这是输出:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main.Reporte.jButton1ActionPerformed(Reporte.java:254)
at Main.Reporte.access$000(Reporte.java:17)
at Main.Reporte$1.actionPerformed(Reporte.java:78)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$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:729)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
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:702)
at java.awt.EventQueue$4.run(EventQueue.java:700)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Answer 1

您的字符串数组未正确实例化。您需要像这样实例化它:

String[] na = new String[100];

如果您不知道数组有多大，您可能需要考虑使用 ArrayList

ArrayList<String> na = new ArrayList<String>();

然后每个字符串都可以添加:

na.add(res.getString(a+1));