public void valueChanged(TreeSelectionEvent e)
            {//重写valueChanged方法
                DefaultMutableTreeNode cdmtn=//得到选中节点对象
                (DefaultMutableTreeNode)e.getPath().getLastPathComponent();
                NodeValue cnv=(NodeValue)cdmtn.getUserObject();//得到自定义节点对象
                if(cnv.classCode==0)
                {//选中节点是根节点时                           
                    cl.show(jpy,"root");
                }
                else if(cnv.classCode==1)
                {//选中节点是分组节点时                                                            
                    String group=cnv.toString();
                    jlGroup.setText(group);
                    cl.show(jpy,"group");
                }
                else if(cnv.classCode==2)
                {//选中节点是某一联系人节点时                           
                    String sql="select pid,pname,pgender,page,pnumber,pemail,pgroup,ppostalcode,"+
            "padress from lxy where uid='"+MainFrame.this.uname+"'and pname='"+cnv.toString()+"'";                                                        
                    setInfo(DButil.getPerInfo(sql));//从数据库得到此联系人信息并设置到信息面板                                    
                    cl.show(jpy,"Info");
                }
                else if(cnv.classCode==3)
                {//相册预览                    
                    jpyview.removeAll();//清空相册预览面板
                    cl.show(jpy,"tpyl");//显示相册预览面板                                                                        
                    viewPic(cdmtn);//预览相册                                                                                
                }
                else if(cnv.classCode==4)
                {//图片明细
                    cl.show(jpy,"tpmx");//显示图片明细面板
                    NodeValue pnv=//得到选中照片的自定义节点对象
                    (NodeValue)((DefaultMutableTreeNode)cdmtn).getUserObject();   
                    detailPic(pnv.value);//点击某一张图片
                }
            }
上面的这句(DefaultMutableTreeNode)cdmtn)我觉得没有必要吧，因为上面已经声明了将cdmtn为DefaultMutableTreeNode类型了吧，请各位指教！！

你去掉试试不就清楚了嘛。
你的排版有待改进，太密集了不方便看。