Java：java.lang.ArrayIndexOutOfBoundsException：-1在JList中删除元素时

Question

所以我使用的是这段代码：

String item = dls.getElementAt(mem_list.getSelectedIndex()).toString();
contentPanel.setVisible(false);
removeMemory(userId_acc, item); 
dls.clear();
List nls = getMems(userId_acc);
dls = new DefaultListModel();

for(int a = 0; a < nls.size(); a++){
    dls.addElement(nls.get(a));
}

mem_list.setModel(dls);

item =要删除的项目（String）
removeMemory（）=删除内存的DB函数
dls = list model
mem_list = jList。

所以当清单清除时：

我明白了：

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1
    at java.util.Vector.elementData(Vector.java:734)
    at java.util.Vector.elementAt(Vector.java:477)
    at javax.swing.DefaultListModel.getElementAt(DefaultListModel.java:89)
    at MemClient$2.valueChanged(MemClient.java:254)
    at javax.swing.JList.fireSelectionValueChanged(JList.java:1796)
    at javax.swing.JList$ListSelectionHandler.valueChanged(JList.java:1810)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:184)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:164)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:211)
    at javax.swing.DefaultListSelectionModel.removeIndexInterval(DefaultListSelectionModel.java:677)
    at javax.swing.plaf.basic.BasicListUI$Handler.intervalRemoved(BasicListUI.java:2601)
    at javax.swing.AbstractListModel.fireIntervalRemoved(AbstractListModel.java:179)
    at javax.swing.DefaultListModel.clear(DefaultListModel.java:510)
    at MemClient.jButton6ActionPerformed(MemClient.java:1109)
    at MemClient.access$700(MemClient.java:57)
    at MemClient$8.actionPerformed(MemClient.java:576)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
    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:6527)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6292)
    at java.awt.Container.processEvent(Container.java:2234)
    at java.awt.Component.dispatchEventImpl(Component.java:4883)
    at java.awt.Container.dispatchEventImpl(Container.java:2292)
    at java.awt.Component.dispatchEvent(Component.java:4705)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
    at java.awt.Container.dispatchEventImpl(Container.java:2278)
    at java.awt.Window.dispatchEventImpl(Window.java:2739)
    at java.awt.Component.dispatchEvent(Component.java:4705)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
    at java.awt.EventQueue.access$400(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:697)
    at java.awt.EventQueue$3.run(EventQueue.java:691)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:719)
    at java.awt.EventQueue$4.run(EventQueue.java:717)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

我也尝试从列表中删除一个项目，但错误是相同的。

这是首次创建和填充mem_list的代码：

mem_list.addListSelectionListener(new ListSelectionListener(){
    @Override
    public void valueChanged(ListSelectionEvent e){
        int sl_row = ((JList) e.getSource()).getSelectedIndex();

        if(e.getValueIsAdjusting() == false){
            LoadMemory(dls.getElementAt(sl_row).toString());
        }
    }
});