Java Swing JFileChooser过滤器不适用于sqlite

import java.io.File;
import javax.swing.filechooser.FileFilter;

public class SQLiteFileFilter extends FileFilter {
    @Override
    public boolean accept(File file) {
        if (file.isDirectory()) {
            return true;
        }
        String extension = getFileExtension(file);
        if (extension != null && (extension.equals("db") || extension.equals("sqlite"))) {
            return true;
        }
        return false;
    }

    @Override
    public String getDescription() {
        return "SQLite Database Files (*.db, *.sqlite)";
    }

    private String getFileExtension(File file) {
        String name = file.getName();
        int lastIndexOf = name.lastIndexOf(".");
        if (lastIndexOf == -1 || lastIndexOf == 0) {
            return null;
        }
        return name.substring(lastIndexOf + 1);
    }
}

import javax.swing.JFileChooser;
import javax.swing.JFrame;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        JFileChooser fileChooser = new JFileChooser();
        fileChooser.setFileFilter(new SQLiteFileFilter());
        frame.add(fileChooser);
        frame.pack();
        frame.setVisible(true);
    }
}