How to use mkdirs in a thread safe manner in Java?

Question

After experiencing issues with mkdirs() and poking around the interwebs, I get the impression that there are thread safety issues with mkdirs().

Is there a way to ensure

Answer 1

One possible solution would be a MkDirService (illustrated below) that guarantees only one instance and runs in it's own thread. Making use of BlockingQueue.

First the Service:

package mkdir;

import java.io.File;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

public class MkDirService extends Thread {

    private static MkDirService service;
    private BlockingQueue pendingDirs = new LinkedBlockingQueue();
    private boolean run = true;

    private MkDirService() {
    }

    public synchronized static MkDirService getService() {
        if (service == null) {
            service = new MkDirService();
            new Thread(service).start();
        }
        return service;
    }

    public void makeDir(File dir) {
        pendingDirs.add(dir);
    }

    public void shutdown() {
        run = false;
    }

    @Override
    public void run() {
        while (run || !pendingDirs.isEmpty()) {
            File curDir = null;
            try {
                curDir = pendingDirs.take();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            if (curDir != null && !curDir.exists()) {
                curDir.mkdir();
                System.out.println("Made: " + curDir.getAbsolutePath());
            }
        }
    }
}

The the Test:

package mkdir;

import java.io.File;

public class MkDirServiceTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        MkDirService mdServ = MkDirService.getService();
        mdServ.makeDir(new File("test1"));
        mdServ.makeDir(new File("test1/test2"));
        mdServ.makeDir(new File("test1/test3"));
        mdServ.shutdown();

    }
}