试图从 DefaultListModel 对象中删除一个元素

Question

using java version 9 I have some test code to remove a item from a list created by passing a refrence to by DefaultListModel. This is what I do.

1. create a DefaultListModel object
2. add 8 elements to it (A..H) by calling addElement
3. remove a item by calling removeElement
4. create a Jlist pass a reference of my DefaultListModel to it

5. The list box displays all 8 items, nothing got removed. code

    philosophers = new DefaultListModel<String>(); philosophers.addElement( "A" ); philosophers.addElement( "B" ); philosophers.addElement( "C" ); philosophers.addElement( "D" ); philosophers.addElement( "E" ); philosophers.addElement( "F" ); philosophers.addElement( "G" ); philosophers.addElement( "H" ); philosophers.removeElement(1); lista = new JList<String>( philosophers );

Answer 1

When ever you have an issue, hit the JavaDocs...

DefaultListModel#removeElement

 public boolean removeElement(Object obj)

Removes the

first (lowest-indexed) occurrence of the argument from this list.


obj - the component to be removed

The interesting point here is, the parameter is an Object , not a index. This means, with Java's auto-boxing, you're actually trying to remove a Integer(1) , which does't exist in the model.

Instead, if you did something like philosophers.removeElement("B"); , you might have had more luck.

However, if we read a little more into the JavaDocs we find

DefaultListModel#remove

 public E remove(int index)

Removes the element at the

specified position in this list. Returns the element that was removed from the list.

Throws an ArrayIndexOutOfBoundsException if the index is out of range (index < 0 || index >= size()).

index - the index of the element to removed

Ah, that sounds more like what you're after