More Swing components - An Introduction to Graphical User Interfaces with Java Swing - page 173

user can implement the interface ListModel for this purpose. However, there is
a predefined implementation of list models in class DefaultListModel which is
sufficient for many purposes. In a list with n entries, the list entries are numbered
0

, ,..., −

1, where 0 denotes the first (topmost) entry. When a list element is
added or removed then the numbering is updated. In the following we describe
class DefaultListModel which is located in the javax.swing library.

1 n

DefaultListModel()

int size()
boolean contains(Object entry)
Object get( int position)
void insertElementAt(Object entry, int position)
void addElement(Object entry)
void removeElementAt( int position)
boolean removeElement(Object entry)
void removeAllElements()

DefaultListModel() is the constructor which creates a list model without any
entries.

size() returns the number of entries currently in the list model.
contains(Object entry) returns true if object entry is in the list model, and
false otherwise.
get(int position) returns the list entry at position position . Throws an ex-
ception if position is negative or greater than or equal to the current number
of list entries. As the return type is Object ,anexplicit cast to the correct type
might be needed.

insertElementAt(Object entry, int position) adds entry entry at position
position to the list model. Throws an exception if position is an invalid
index.

addElement(Object entry) adds an entry at the end of the list.

removeElementAt(int position) removes the entry at position position .
Throws an exception if position is an invalid index. The remaining list entries
are renumbered to maintain a consecutive indexing.

removeElement(Object entry) removes the entry entry .Ifsuccessful true is
returned, otherwise false is returned.
removeAllElements() removes all entries from the list model.

Once the list model is defined, one passes it to a JList in the constructor or by
using the set -method:

JList(ListModel lModel)
setModel(ListModel lModel)