Problemas atualizando JList

package jlistteste;

import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.DefaultListModel;

public class lixo extends javax.swing.JFrame {

	public lixo() {
		initComponents();
		Qualquer ref = new Qualquer();
		(new Thread(ref)).start();
	}

	@SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        nameList = new javax.swing.JList();
        addButton = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jScrollPane1.setViewportView(nameList);

        addButton.setText("Adicionar");
        addButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                addButtonActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.CENTER)
                    .addComponent(addButton)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 250, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 245, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(addButton)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

	private void addButtonActionPerformed(java.awt.event.ActionEvent evt) {
		listaDeAlgumaCoisa.add("Lixo");
		System.out.println("Tam: " + listaDeAlgumaCoisa.size());
	}

	public static void main(String args[]) {
		java.awt.EventQueue.invokeLater(new Runnable() {

			public void run() {
				new lixo().setVisible(true);
			}
		});
	}

	private class Qualquer implements Runnable {

		DefaultListModel modelo = new DefaultListModel();
		private List<String> lista = null;
		boolean atualiza = false;
		int tam = 0;

		public void run() {
			while (true) {
				lista = listaDeAlgumaCoisa;
				tam = lista.size();
				if (modelo.size() == tam) {
					for (int i = 0; i < tam; i++) {
						if (lista.get(i).compareTo((String) modelo.get(i)) != 0) {
							atualiza = true;
							break;
						}
					}
				} else {
					atualiza = true;
				}

				if (atualiza) {
					modelo.clear();

					for (int i = 0; i < tam; i++) {
						modelo.addElement(lista.get(i));
					}

					nameList.setModel(modelo);

					atualiza = false;
				}
				try {
					Thread.sleep(1000);
				} catch (InterruptedException ex) {
					Logger.getLogger(lixo.class.getName()).log(Level.SEVERE, null, ex);
				}
			}
		}
	}
	private List<String> listaDeAlgumaCoisa = new ArrayList<String>();
    // Variables declaration - do not modify
    private javax.swing.JButton addButton;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JList nameList;
    // End of variables declaration
}