e759. adding and removing an item in a jcombobox component.txt

这里面包含了一百多个JAVA源文件

There is no method for replacing an item. To replace an item, first remove the item and then insert the new one. 
    // Create a read-only combobox; the combobox is read-only
    // in that it does not allow the user to type in a new item.
    // The combobox still allows programmatic changes to its items.
    String[] items = {"item1", "item2"};
    JComboBox cb = new JComboBox(items);
    
    // Add an item to the start of the list
    cb.insertItemAt("item0", 0);
    
    // Add an item after the first item
    cb.insertItemAt("item0.5", 1);
    
    // Add an item to the end of the list
    cb.addItem("item3");
    
    // Remove first item
    cb.removeItemAt(0);
    
    // Remove the last item
    cb.removeItemAt(cb.getItemCount()-1);
    
    // Remove all items
    cb.removeAllItems();