How to make sure that only a single instance of a Java application is running?

Question

I want my application to check if another version of itself is already running.

For example, demo.jar started, user clicks to run it again, but the sec

Answer 1

Following solution work in two deadly scenerio too. 1> Even your launched exe scheduled as javaw.exe in task manager. 2> You can install your application at two location and from launching both location it also works.

String tempDir = System.getProperty("java.io.tmpdir");// dependent to OS find any tem dir.
        String filePath = tempDir + "lockReserverd.txt";
        try {
            final File file = new File(filePath);

            if(file.exists())
                return false;

            final RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
            final FileLock fileLock = randomAccessFile.getChannel().tryLock();
            if (fileLock != null) {
                Runtime.getRuntime().addShutdownHook(new Thread() {
                    public void run() {
                        try {
                            fileLock.release();
                            randomAccessFile.close();
                            file.delete();
                        } catch (Exception e) {
                            //log.error("Unable to remove lock file: " + lockFile, e);
                        }
                    }
                });
                return true;
            }
        } catch (Exception e) {
            //log.Error("Unable to create and/or lock file");
        }
        return false

or

This will work if your application.exe is listed in task manager

"tasklist /FI \"IMAGENAME eq "+MyApplication+".exe