javaMultithreading

Characteristics

Multithreading enables parallel or concurrent data processing for the implementation of functional requirements of the system:Company.

Illustration

The data model is implemented as POJOs, as usual. A sequential implementation of the operations for totaling and cutting salaries is also included. For instance:

/**
 * A company has a name and consists of (possibly nested) departments.
 */
public class Company {
    
    private String name;
    private List<Department> depts = new LinkedList<Department>();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Department> getDepts() {
        return depts;
    }

    /**
     * Compute total, sequentially
     */
    public Double total() {
        double total = 0;
        for (Department d : getDepts()) {
            total += d.total();
        }
        return total;
    }

    /**
     * Perform cut, sequentially
     */
    public void cut() {
        for (Department d : getDepts()) {
            d.cut();
        }
    }

}

Concurrent computations rely on the identification of actions suitable for multithreading. Department-level actions for totaling and cutting salaries are chosen as the scope here. The following context class shows how an action is not performed sequentially but rather by submission to a thread pool.

/**
 * Run an action via submission to thread pool, i.e., concurrently
 */
public class ConcurrentContext implements Context {

    private static final int POOL_SIZE = 7;

    private ExecutorService pool;

    public ConcurrentContext() {
        pool = Executors.newFixedThreadPool(POOL_SIZE);
    }

    public synchronized <X, Y> void execute(final Action<X, Y> action,
            final X param) {

            final ConcurrentContext context = this;
            pool.submit(new Runnable() {
                public void run() {
                    action.execute(context, param);

                }
            });

    }

    public void waitForTermination() {
        try {
            pool.awaitTermination(2, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

}

Architecture

The contribution follows a standardized structure:

inputs contains input files for tests
src/main/java contains the following packages:
- org.softlang.company.features for implementations of functional requirements.
  - org.softlang.company.features.action for helper classes for Feature:Total and Feature:Cut.
  - org.softlang.company.features.context for helper classes for Multithreading.
- org.softlang.company.model for implementations of Feature:Company.
src/test/java contains the following packages:
- org.softlang.company.tests for Technology:JUnit test cases.