large virtual lists in Swing using AbstractListModel -- limit at 119,000,000 items?

Question

I've got my "virtual list" in swing working well, but it seems to fail when I exceed some particular number of items. By "fail" I mean that the scroll bar magically vanishes when the number of items is > Nmax, and it comes back when the number of items is <= Nmax; Nmax seems to be somewhere around 119,304,000 on my system.

What am I running up against?!?!

(Here's a test program: on my computer, if I type in 119,304 it works ok, but I click the up arrow and the scroll bar disappears)

package com.example.test;

import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSpinner;
import javax.swing.SpinnerModel;
import javax.swing.SpinnerNumberModel;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

// based on:
// http://www.java2s.com/Tutorial/Java/0240__Swing/extendsAbstractListModel.htm
// http://www.java2s.com/Tutorial/Java/0240__Swing/SpinnerNumberModel.htm
// http://java.sun.com/j2se/1.4.2/docs/api/javax/swing/SpinnerNumberModel.html
// http://www.java2s.com/Tutorial/Java/0240__Swing/ListeningforJSpinnerEventswithaChangeListener.htm
// http://java.sun.com/products/jfc/tsc/tech_topics/jlist_1/jlist.html

public class BigVirtualList extends JFrame {

    public static void main(String[] args) {
     new BigVirtualList();
    }

    static final int initialLength = 1;
    final private JList list1 = new JList();
    final private BVLData bvldata = new BVLData(initialLength*1000);

    public BigVirtualList() {
     this.setTitle("Big virtual list");
     this.getContentPane().setLayout(new BorderLayout());
     this.setSize(new Dimension(400, 300));
     list1.setModel(bvldata);

     list1.setPrototypeCellValue(list1.getModel().getElementAt(0));


     SpinnerModel model1 = new SpinnerNumberModel(initialLength,1,1000000,1);
     final JSpinner spinner1 = new JSpinner(model1);

     this.getContentPane().add(new JScrollPane(list1), BorderLayout.CENTER);
     JLabel label1 = new JLabel("Length (1000s of items):");
     JPanel panel1 = new JPanel(new BorderLayout());
     panel1.add(label1, BorderLayout.WEST);
     panel1.add(spinner1, BorderLayout.CENTER);
     this.getContentPane().add(panel1, BorderLayout.SOUTH);  

     ChangeListener listener = new ChangeListener() {
      public void stateChanged(ChangeEvent e) {
       Integer newLength = (Integer)spinner1.getValue();
       bvldata.setLength(newLength*1000);
      }
     };

     spinner1.addChangeListener(listener);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setVisible(true);
    }
}

class BVLData extends AbstractListModel {
    public BVLData(int length) { this.length = length; }

    private int length;

    public int getLength() { return length; }
    public void setLength(int length) {
     int oldLength = getLength();
     this.length = length;
     int newLength = getLength();

     if (newLength > oldLength)
      fireIntervalAdded(this, oldLength+1, newLength);
     else if (newLength < oldLength)
      fireIntervalRemoved(this, newLength+1, oldLength);  
    } 

    @Override
    public Object getElementAt(int index) {
     return "Item "+index+" mod 107 = "+(index%107);
    }

    @Override
    public int getSize() { return getLength(); }

}

Answer 1

Well I don't see the purpose but anyway ...

I guess you break the integer max value somewhere in the scroll pane:

System.out.println("CellHeight:"+list1.getFixedCellHeight());
System.out.println("CellHeight*119304000:"+NumberFormat.getNumberInstance().format(list1.getFixedCellHeight()*119304000.0));
System.out.println("MAXINT:"+Integer.MAX_VALUE);

Gives you the numbers:

CellHeight:18
CellHeight*119304000:2.147.472.000
MAXINT:2.147.483.647

As you can see adding another 18000 pixel in height will go beyond MAXINT ... this gets you in trouble.