ggalmazor

void read_frequency() {
    if (Serial.available() <= 0)
        return;

    String description = read_serial_message(0xFD);

    if (!is_valid(description))
        return;

    return parse_frequency(description);

ggalmazor

Keybase proof

I hereby claim:

• I am ggalmazor on github.
• I am ggalmazor (https://keybase.io/ggalmazor) on keybase.
• I have a public key ASAbZuXpyLdy8y8QZR-YKb2L5yVNgcFhlzkWN3dgyNr8MAo

To claim this, I am signing this object:

ggalmazor

Stopping background jobs: a Java parallel code refactoring case

I spend most of my working day helping to maintain and evolve the awesome OpenDataKit tool kit, which includes ODK Briefcase, a Java desktop application (Swing) that takes care of pulling, pushing and exporting forms.

Before continuing, I feel like I should give a disclaimer. It's a long post that's served me to put my thoughts together and fix in my head what I've learned. You could read on and miss some obvious and much simpler solution to some problem. If that happens, please, please, write a comment! I'm not trying to write any foundational text. I'm just a guy figuring out how to do parallel jobs in Java, and I'm probably wrong.

The challenge

Briefcase interacts with servers that store blank forms and answered form submissions using an HTTP API to download them to a user's computer for post-processing.

ggalmazor

public class Job<T> {
  private final JobAwareSupplier<T> block;

  private Job(JobAwareSupplier<T> block) {
    this.block = block;
  }

  public static <U> Job<U> supply(JobAwareSupplier<U> supplier) {
    return new Job<>(supplier);
  }

ggalmazor

public ExecutorService pull(List<FormStatus> forms) {
  ExecutorService executor = new ForkJoinPool(
      commonPool().getParallelism(),
      commonPool().getFactory(),
      this::handleError,
      commonPool().getAsyncMode()
  );

  forms.stream()
      .map(form -> pullOne(form, executor))

ggalmazor

public class ExportPanelForm {
  private static final String EXPORTING = "Exporting";
  private static final String DOT = ".";
  private JLabel exportingLabel;

  public void updateExportingLabel() {
    String newText = cycle(exportingLabel.getText(), 19);
    exportingLabel.setText(newText);
  }

ggalmazor

public class ExportPanelForm {
  private JLabel exportingLabel;

  public void updateExportingLabel() {
    String text = exportingLabel.getText();
    if (text.equals("Exporting..........")) {
      text = "Exporting.";
    } else {
      text += ".";
    }

ggalmazor

public class ExportPanelForm {
  private static final String EXPORTING = "Exporting";
  private static final String DOT = ".";
  private JLabel exportingLabel;

  public void updateExportingLabel() {
    String text = exportingLabel.getText();
    if (text.equals(EXPORTING + DOT + DOT + DOT + DOT + DOT + DOT + DOT + DOT + DOT + DOT)) {
      text = EXPORTING + DOT;
    } else {