Continue a visit of SimpleFileVisitor

Question

I'm not sure if I'm using the right approach so I'm open to new ideas before telling me that i'm doing it wrong. I have an array of directories path that I need to look for files. Let's say all .txt at example. Now I run a Files.walkFileTree(...) on every directory and with the SimpleFileVisitor that stops at first match. But now i want to add a next button that keeps searching from the point I stop. How can I do this?

I've thought that I could save all matches on a array and then read it from there but it's space and memory consuming. So a better idea would be appreciate.

// example paths content: [/usr, /etc/init.d, /home]
ArrayList<String> paths; 
for( String s : paths )
    Files.walkFileTree(Paths.get(s), new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            if (alreadyfound >= 10) {
                return FileVisitResult.TERMINATE;
            }
            if (file.toString().endsWith(".txt")) {
                System.out.println("Found: " + file.toFile());
            }
            return FileVisitResult.CONTINUE;
        }
    });

Answer 1

I once wrote a class that should do exactly what you described. I solved it by running the FileVisitor in its own Thread. When a file was found with a desired extension it simply stopped execution with wait() until a button signaled to continue with notify().

public class FileSearcher extends Thread{
    private Object lock = new Object();
    private Path path;
    private JLabel label;
    private String extension;

    public FileSearcher(Path p, String e, JLabel l){
        path = p;
        label = l;
        extension = e;
    }       
    public void findNext(){
        synchronized(lock){
            lock.notify();
        }   
    }   
    @Override
    public void run() {
        try {
            Files.walkFileTree(path, new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                    if(file.toString().toLowerCase().endsWith(extension)){
                        label.setText(file.toString());
                        synchronized(lock){
                            try {
                                lock.wait();
                            } catch (InterruptedException e1) {
                                e1.printStackTrace();
                            }
                        }
                    }
                    return FileVisitResult.CONTINUE;
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }       
    }
}

A simple example how to use it would be this

JFrame frame = new JFrame();
JPanel panel = new JPanel();
panel.setLayout(new FlowLayout());
JLabel label = new JLabel();
FileSearcher fileSearcher = new FileSearcher(Paths.get("c:\\bla"), ".txt", label);
JButton button = new JButton();
button.setText("next");
button.addActionListener(new ActionListener(){
    @Override
    public void actionPerformed(ActionEvent arg0) {
        fileSearcher.findNext();
    }});
panel.add(label);
panel.add(button);
frame.add(panel);
frame.setSize(300, 300);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
fileSearcher.start();