Ok, so I wrote a very simple programme, just to practice multithreading.

I know it can be coded better, but I'm still learning about this, so please be lenient.

This is my code so far:

package threads;

// Create a thread
import java.io.File;

class threads implements Runnable {
    // This should scan the directory every 2 minutes

    Thread masterThread;

    threads() {
        // Create a second thread - this thread will handle the files found in the folder
        masterThread = new Thread(this, "first child");
        masterThread.start();
    }

    // Entry point for second thread
    public void run() {
        // TODO:: Make more threads
        Thread currentThread = Thread.currentThread();
        Thread firstThread = new Thread();
        Thread secondThread = new Thread();
        String fileName = "";

        while (masterThread == currentThread) {
            // Scan the folders, assign the files to threads for processing
            File main_dir = new File("C:\\Thread test");

            File[] child_dirs = main_dir.listFiles();

            for (int i = 0; i < child_dirs.length; i++) {
                // [get filename] dir_name = child_files[i].getName();
                // start thread to look for files in this dir.
                File[] new_files = child_dirs[i].listFiles();
                // create threads for each of the contained files, up to a limit of 3 threads.
                for (int ii = 0; ii < new_files.length; ii++) {
                    fileName = new_files[ii].getName();
                    if (!firstThread.isAlive()) {
                        // Assign firstThread the task of handling the file
                        firstThread.start();
                    } else if (!secondThread.isAlive()) {
                        // Assign secondThread the task of handling the file
                        secondThread.start();
                    }
                }
            }

            while (firstThread == currentThread) {
                try {
                    // Handle file
                    File file = new File(fileName);
                    // Destination directory
                    File dir = new File("C:\\Thread test\\retain");
                    // Move file to new directory
                    boolean success = file.renameTo(new File(dir, file.getName()));
                    System.out.println(fileName + " was moved succesfully");
                    if (!success) {
                        System.out.println(fileName + " was not moved succesfully");
                    }
                    Thread.sleep(5000);
                } catch (InterruptedException ie) {
                    ie.printStackTrace();
                }
            }

            while (secondThread == currentThread) {
                try {
                    //Handle file
                    File file = new File(fileName);
                    // Destination directory
                    File dir = new File("C:\\Thread test\\retain");
                    // Move file to new directory
                    boolean success = file.renameTo(new File(dir, file.getName()));
                    System.out.println(fileName + " was moved succesfully");
                    if (!success) {
                        System.out.println(fileName + " was not moved succesfully");
                    }
                    Thread.sleep(5000);
                } catch (InterruptedException ie) {
                    ie.printStackTrace();
                }
            }
        }
    }

    class ThreadStarter {

        [B]public static void main(String[] args) {[/B]
            // This thread will scan the folders every 2 minutes, and assign other threads to handle files found in the directories
            new threads();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

I marked the one line bold
(this line)

public static void main(String[] args) {

because I get an error on that line that keeps me from compiling.

Here is the error:
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - inner classes cannot have static declarations
at threads.threads$ThreadStarter.main(threads.java:88)

I'm pretty confused. I've been browsing around trying to find out what's causing it, but no luck so far. Was wondering if someone here at DaniWeb could lend me a hand?

Because in the same file, you declare 2 classes:

class threads implements Runnable {
  threads() {

  }

class ThreadStarter {

}
}

You don't need a separate inner class for the main. Just put it in the threads class

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