请问有没有从把panel上的swing component的方法

Question

remove
public void remove(int index)Removes the component, specified by index, from this container. Parameters:
index - the index of the component to be removed.
Since:
JDK1.1 
See Also:
add(java.awt.Component)--------------------------------------------------------------------------------remove
public void remove(Component comp)Removes the specified component from this container. Parameters:
comp - the component to be removed
See Also:
add(java.awt.Component)--------------------------------------------------------------------------------removeAll
public void removeAll()Removes all the components from this container. See Also:
add(java.awt.Component), remove(int)

Answer 1

if(cfgsysadmin == selectedNode)
     {if(temppanel != null)
      jpanel.removeAll();
      if(demo == null)
      demo = new CfgSysadmini();
      temppanel = demo.getDemoPanel();
      jpanel.add(demo.getDemoPanel(), BorderLayout.NORTH);
      this.validate();
     }
     else if(sqlsysadmin == selectedNode )
     {
      if(temppanel != null)
      jpanel.removeAll();
      if(demo == null)
      demo = new SqlSysadmin();
      temppanel = demo.getDemoPanel();
      jpanel.add(demo.getDemoPanel(), BorderLayout.CENTER);
      this.validate();
     }
显示不出第二次加入的component