Black Friday Orders Manager in Java

Score: 100 / 100

Table of Contents

• Black Friday Orders Manager in Java
  • Table of Contents
  • Threads
    • Main Thread
    • Level 1 Threads
    • Level 2 Threads
  • Synchronisation

Threads

Main Thread

The Main class Tema2.java has the responsability of creating all of the level 1 threads MasterEmployee and putting them in a pool of threads with a fixed size of P (masterPool). Then, it waits for all level 1 threads to finish in order to not close the output files before all of them finish processing them. The method which puts level 1 threads into the pool is called:

private static void InitThreadHandlers(final String[] args)

and the logic behind it is explained in the following code snippet:

// initialize the level 1 threads
ArrayList<MasterEmployee> masterEmployees =
  new ArrayList<>(
    Stream.generate(() -> new MasterEmployee())
      .limit(P)
      .collect(Collectors.toList())
  );

// submit them
for (MasterEmployee masterEmployee : masterEmployees) {
   masterPool.submit(masterEmployee);
}

// wait for them to finish before closing the output files
for (MasterEmployee masterEmployee : masterEmployees) {
    masterEmployee.join();
}

Level 1 Threads

A level 1 thread is represented by the MasterEmployee.java class. This type of thread reads lines from the orders.txt file and then starts spawning into the level 2 thread pool (lesserPool), which also has a fixed size of P and is shared between all level 1 threads. It then waits for its level 2 threads to finish before "shipping" its order.

// initialize the level 2 threads
ArrayList<LesserEmployee> lesserEmployees =
    new ArrayList<>(
     Stream.generate(() -> new LesserEmploye(ORDER_ID, productsLeft, productsReader))
        .limit(NR_PRODUCTS)
        .collect(Collectors.toList())
     );

// submit them
for (LesserEmployee lesserEmployee : lesserEmployees) {
    Tema2.lesserPool.submit(lesserEmployee);
}

// wait for them to finish before shipping the order
for (LesserEmployee lesserEmployee : lesserEmployees) {
    lesserEmployee.join();
}

Level 2 Threads

A level 2 thread is represented by the LesserEmployee.java class. This thread works by reading the order_products_out.txt file line by line. Once it finds a product corresponding to the level 1 thread that spawned it, it "ships" the product before finishing its execution.

Synchronisation

This part is explained in the README_BONUS.md file.