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.