我不知道为什么，但是这段代码会导致StackOverflowError：
public void update() {
DefaultListModel lm = new DefaultListModel();
if (elements != null)
for (String elem : elements) {
lm.addElement(lm);
}
jList1.setModel(lm);
repaint();
}
我尝试调试此错误，实际上stackOverflowError发生在外部（我想在AWT事件队列中...。），这是我在控制台中看到的内容：
首先多次：
at javax.swing.DefaultListModel.toString(DefaultListModel.java:397)
at java.lang.String.valueOf(String.java:2826)
at java.lang.StringBuilder.append(StringBuilder.java:115)
at java.util.AbstractCollection.toString(AbstractCollection.java:422)
at java.util.Vector.toString(Vector.java:940)
at javax.swing.DefaultListModel.toString(DefaultListModel.java:397)
at java.lang.String.valueOf(String.java:2826)
然后重复此操作（全部在同一堆栈跟踪中）：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at java.awt.Window.dispatchEventImpl(Window.java:2476)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.paint(BasicTabbedPaneUI.java:770)
at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
at javax.swing.JComponent.paintComponent(JComponent.java:752)
at javax.swing.JComponent.paint(JComponent.java:1029)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5131)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1479)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1410)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
at java.awt.Container.paint(Container.java:1780)
at java.awt.Window.paint(Window.java:3375)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.paint(BasicTabbedPaneUI.java:770)
at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
at javax.swing.JComponent.paintComponent(JComponent.java:752)
at javax.swing.JComponent.paint(JComponent.java:1029)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5131)
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1479)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1410)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
at java.awt.Container.paint(Container.java:1780)
at java.awt.Window.paint(Window.java:3375)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:86)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.layoutContainer(BasicTabbedPaneUI.java:2384)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:89)
at javax.swing.plaf.basic.BasicTabbedPaneUI.setRolloverTab(BasicTabbedPaneUI.java:558)
at javax.swing.plaf.basic.BasicTabbedPaneUI.access$2000(BasicTabbedPaneUI.java:37)
at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mouseMoved(BasicTabbedPaneUI.java:3645)
at java.awt.Component.processMouseMotionEvent(Component.java:6312)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3285)
at java.awt.Component.processEvent(Component.java:6036)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4630)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4251)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:86)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.layoutContainer(BasicTabbedPaneUI.java:2384)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:89)
at javax.swing.plaf.basic.BasicTabbedPaneUI.setRolloverTab(BasicTabbedPaneUI.java:558)
at javax.swing.plaf.basic.BasicTabbedPaneUI.access$2000(BasicTabbedPaneUI.java:37)
at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mouseMoved(BasicTabbedPaneUI.java:3645)
at java.awt.Component.processMouseMotionEvent(Component.java:6312)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3285)
at java.awt.Component.processEvent(Component.java:6036)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4630)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4251)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.SizeRequirements.calculateAlignedPositions(SizeRequirements.java:444)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:415)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validateTree(Container.java:1513)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:86)
at javax.swing.plaf.basic.BasicTabbedPaneUI$TabbedPaneLayout.layoutContainer(BasicTabbedPaneUI.java:2384)
at java.awt.Container.layout(Container.java:1421)
at java.awt.Container.doLayout(Container.java:1410)
at java.awt.Container.validateTree(Container.java:1507)
at java.awt.Container.validate(Container.java:1480)
at javax.swing.plaf.basic.BasicTabbedPaneUI.ensureCurrentLayout(BasicTabbedPaneUI.java:1429)
at javax.swing.plaf.basic.BasicTabbedPaneUI.getTabBounds(BasicTabbedPaneUI.java:1449)
at com.sun.java.swing.plaf.windows.WindowsTabbedPaneUI.setRolloverTab(WindowsTabbedPaneUI.java:89)
at javax.swing.plaf.basic.BasicTabbedPaneUI.setRolloverTab(BasicTabbedPaneUI.java:558)
at javax.swing.plaf.basic.BasicTabbedPaneUI.access$2000(BasicTabbedPaneUI.java:37)
at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mouseMoved(BasicTabbedPaneUI.java:3645)
at java.awt.Component.processMouseMotionEvent(Component.java:6312)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3285)
at java.awt.Component.processEvent(Component.java:6036)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4630)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4251)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" Exception in thread "AWT-EventQueue-0"
任何的想法？
最佳答案
您正在将列表作为元素添加到其自身，当您尝试将其递归转换为String时，这当然会导致无限递归：
lm.addElement(lm);
您可能是这个意思：
lm.addElement(elem);
解决此问题后，
NullPointerException可能会消失，或者可能完全不相关。