Prevent launching multiple instances of a java application

Question

I want to prevent the user from running my java application multiple times in parallel.

To prevent this, I have created a lock file when am opening the application,

Answer 1

There are already available java methods in File class to achieve the same. The method is deleteOnExit() which ensure the file is automatically deleted when the JVM exits. However, it does not cater to forcible terminations. One should use FileLock in case of forcible termination.

For more details check, https://docs.oracle.com/javase/7/docs/api/java/io/File.html

Thus code snippet which could be used in the main method can be like :

public static void main(String args[]) throws Exception {

    File f = new File("checkFile");

    if (!f.exists()) {
        f.createNewFile();
    } else {
        System.out.println("App already running" );
        return;
    }

    f.deleteOnExit();

    // whatever your app is supposed to do
    System.out.println("Blah Blah")
}