JList

• A component that allows the user to select one or more objects from a list. A separate model, ListModel, represents the contents of the list.
• JList and ListModel work together to maintain the list.  JList is the visual interface item, ListModel is used to maintain the list, this includes adding items, removing items, and getting item counts.
• Since ListModel is an interface class, you have to use a class that implements it.  For most lists, you can use a class called DefaultListModel.
• To create in Netbeans:
• Since you'll probably want to have scroll bars on the list, add a JScrollPane to your JPanel, then add the JList to it. (version 5.5+ of Netbeans does this for you automatically when you add a JList
  
• Rename the JList to something logical.
  
• Setup the  DefaultListModel for the JList,
  
• Properties of the JList to set in Netbeans include:
• model - you can use the model to preload the list with text strings (as was done for JComboBox), or  setup the model with an instance of DefaultListModel (select custom code option)
• To setup a DefaultListModel,
  
1. import javax.swing.*;
   
2. Open the properites of the JList box
3. press the little square button next to model,
   
4. from the drop down select "Custom Code"
5. in the box, fill in   new DefaultListModel()
   

• selectionMode (under other properties)
• Single - allow the user to select just one thing
• Single-interval - allow the user to select just one contiguous set
• Multiple-interval - allow the user to select multiple items in multiple places
  
• visible row count (under other properties) - set to the number of items to be seen without scrolling
• Programming:
• to add items, you'll first have to get a reference to the DefaultListModel, then use the addElement method

        String name = nameField.getText();
        String phone = phoneField.getText();
        String email = emailField.getText();
        //
        // add to the list box
        //
        Employee emp = new Employee(name, phone, email);   // create an employee object
        DefaultListModel employeemodel = (DefaultListModel)employeeList.getModel();  // get a reference to the list model
        employeemodel.addElement(emp);  // add the employee to the list

• to determine which item is selected, use the getSelectedIndex() method of the JList. This returns the index of the item selected by the user, or -1 if no item is selected.
  
• to remove items, again you'll have to get a reference to the DefaultListModel, then use the remove method.

        DefaultListModel employeemodel = (DefaultListModel)employeeList.getModel();
        int selected = employeeList.getSelectedIndex();
        //
        // remove the selected one
        //
        if(selected >= 0)  // selected is -1 for nothing selected
            employeemodel.remove(selected);  //remove one item
  

• The ListSelectionEvent is triggered whenever a user selects a list item.
• To add code to process this event in Netbeans, do the following:
• right click on the JList (either in the design window or Inspector window)
• From the popup menu select  Events, then ListSelection, then ValueChanged
• Netbeans will then add the method to handle the selection change event.
  
• Other userful methods
  • JList
    • getSelectedIndices() - returns an array of selections for use in Multiple Select and Single interval select models
    • setSelectedIndex and setSelectedIndices - allows your program to preset the selected items.
    • getSelectedValue - returns the first object that is selected
    • getSelectedValues - returns an array of objects that are selected.
      
  • DefaultListModel 
    • clear() - removes all elements from the list
    • removeAllElements() - same as clear()
      
    • size() - returns the number of items in the list
    • add(index, object) - adds an item at a specified index.
    • addElement(object) - adds an object to the end of the list
      
    • get(index) - retrieves the object at the specified index 
    • remove(index) - removes the object at the specified index
    • removeElement(object) - removes the object from the list.
      

• Note1: If you want to add numbers to a list, you can either add them as wrapper class objects (Integer and Double), or as a String.
  
• Note: if you are deleting several items from a JList using the remove method, then the remaining items in the list are renumbered after each remove, therefore you should do the removes in reverse order. E.g. to remove the selected items: