Scheduled Notifications (First Android App)

Question

I'm happy to present my first Android project, which collects market index data (three Asian indices) and fires a notificaiton every Wednesday, Thursday and Friday at 7:30 AM displaying the data.

I've applied to Computer Science in Lund, Sweden. I am looking to improve my Java through Android development (which I've found particularly interesting).

Please consider giving some feedback. I'll be happy with anything!

MainActivity:

public class MainActivity extends AppCompatActivity {
    public static final String CHANNEL_ID = "com.example.morgonnotification.channel";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        createNotificationChannel();
        ReminderReceiver.setNextNotification(this);
    }

    private void createNotificationChannel() {
        NotificationChannel channel = new NotificationChannel(CHANNEL_ID, "Index Channel", NotificationManager.IMPORTANCE_HIGH);
        NotificationManagerCompat.from(this).createNotificationChannel(channel);
    }

}

ReminderReceiver (BroadcastReceiver):

public class ReminderReceiver extends BroadcastReceiver {

    public static void setNextNotification(Context context) {
        AlarmManager alarmManager = (AlarmManager) context.getSystemService(ALARM_SERVICE);
        Intent intent = new Intent(context, ReminderReceiver.class);
        PendingIntent alarmIntent = PendingIntent.getBroadcast(context, 0, intent, 0);

        ZonedDateTime fireTime = ZonedDateTime.now(ZoneId.of("Europe/Stockholm")).withHour(7).withMinute(30).withSecond(0);
        long nowEpochSecond = ZonedDateTime.now(ZoneId.of("Europe/Stockholm")).toEpochSecond();
        long fireTimeEpochSecond = fireTime.toEpochSecond();
        DayOfWeek day = fireTime.getDayOfWeek();

        switch (day.name()) {
            case "WEDNESDAY":
                //before 7:30 on a wednesday? Set alarm to this Wednesday morning
                fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                        fireTime.with(TemporalAdjusters.next(DayOfWeek.THURSDAY));
                break;
            case "THURSDAY":
                //before 7:30 on a Thursday? Set alarm to this Thursday morning
                fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                        fireTime.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));

                break;
            case "FRIDAY":
                //before 7:30 on a Friday? Set alarm to this Friday morning
                fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                        fireTime.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));
                break;
            default:
                fireTime = fireTime.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));
                break;
        }

        if (alarmManager != null)
            alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,
                    fireTime.toInstant().toEpochMilli(), alarmIntent);
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction()) ||
                "android.intent.action.QUICKBOOT_POWERON".equals(intent.getAction()) ||
                intent.getAction() == null) {
            setNextNotification(context);
        }

        StringBuilder indicesBuilder = new StringBuilder();
        Thread thread = new Thread(() -> {
            try {
                Document doc = Jsoup.connect("https://money.cnn.com/data/world_markets/asia//").get();

                Elements nikkei = doc.select("#wsod_indexDataTableGrid > tbody > tr:nth-child(6) > td:nth-child(5) > span > span");
                indicesBuilder.append("N: ").append(nikkei.text()).append(", ");

                Elements shanghaiComposite = doc.select("#wsod_indexDataTableGrid > tbody > tr:nth-child(3) > td:nth-child(5) > span > span");
                indicesBuilder.append(" S: ").append(shanghaiComposite.text()).append(", ");

                Elements hangSeng = doc.select("#wsod_indexDataTableGrid > tbody > tr:nth-child(4) > td:nth-child(5) > span > span");
                indicesBuilder.append(" H: ").append(hangSeng.text());

            } catch (Exception e) {
                indicesBuilder.append("Something went terribly wrong");
                e.printStackTrace();

            } finally {
                Notification notification = new NotificationCompat.Builder(context, MainActivity.CHANNEL_ID)
                        .setSmallIcon(R.drawable.ic_index)
                        .setContentTitle("Morning indices")
                        .setPriority(NotificationCompat.PRIORITY_HIGH)
                        .setStyle(new NotificationCompat.BigTextStyle().bigText(indicessBuilder)).build();

                NotificationManagerCompat manager = NotificationManagerCompat.from(context);
                manager.notify(1, notification);
                indicesBuilder.setLength(0);

            }
        });
        thread.start();

    }
}

XML File:

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <receiver
        android:name=".ReminderReceiver"
        android:enabled="true"
        android:exported="true">
        <intent-filter >
            <action android:name="android.intent.action.BOOT_COMPLETED" />
            <action android:name="android.intent.action.QUICKBOOT_POWERON" />
        </intent-filter>
    </receiver>

    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Answer 1

Welcome to Code Review. Your code seems me well structured, I have two suggestions for you:

switch (day.name()) {
    case "WEDNESDAY":
         //before 7:30 on a wednesday? Set alarm to this Wednesday morning
         fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                 fireTime.with(TemporalAdjusters.next(DayOfWeek.THURSDAY));
                 break;
    case "THURSDAY":
         //before 7:30 on a Thursday? Set alarm to this Thursday morning
         fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                 fireTime.with(TemporalAdjusters.next(DayOfWeek.FRIDAY));
                 break;
    case "FRIDAY":
         //before 7:30 on a Friday? Set alarm to this Friday morning
         fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
                 fireTime.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));
                 break;
    default:
         fireTime = fireTime.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));
                 break;
}

There is code repetition and you have a binary association between one day and another one, so you could create a Map to reduce your code lines like below:

//creation of one map for the days
Map<String, String> map = new HashMap<String, String>();
map.put("WEDNESDAY", "THURSDAY");
map.put("THURSDAY" , "FRIDAY");
map.put("FRIDAY"   , "WEDNESDAY");

//here the code instead of your switch
DayOfWeek day = fireTime.getDayOfWeek();
String name = day.name();
if (map.containsKey(name)) {
    fireTime = (nowEpochSecond < fireTimeEpochSecond) ? fireTime :
               fireTime.with(TemporalAdjusters.next(DayOfWeek.valueOf(map.get(name))));
} else {
    //default value of your switch
    fireTime = fireTime.with(TemporalAdjusters.next(DayOfWeek.WEDNESDAY));
}

About the following lines in your jsoup code :

StringBuilder indicesBuilder = new StringBuilder();
indicesBuilder.append("N: ").append(nikkei.text()).append(", ");
indicesBuilder.append(" S: ").append(shanghaiComposite.text()).append(", ");
indicesBuilder.append(" H: ").append(hangSeng.text());

You can obtain the same result not going crazy about data format when you add or delete new indices using StringJoiner class:

StringJoiner sj = new StringJoiner(", ");
sj.add("N: " + nikkei.text());
sj.add("S: " + shanghaiComposite.text());
sj.add("H: " + hangSeng.text());

String bigText = sj.toString(); //<-- the string you can use later in your code.