added JavaDoc comments

app/src/main/java/fr/free/nrw/commons/Utils.java

@@ -37,12 +37,23 @@ public class Utils {
         }
     }
 
+    /**
+     * Creates an URL for thumbnail
+     *
+     * @param filename Thumbnail file name
+     * @return URL of thumbnail
+     */
     public static String makeThumbBaseUrl(@NonNull String filename) {
         String name = new PageTitle(filename).getPrefixedText();
         String sha = new String(Hex.encodeHex(DigestUtils.md5(name)));
         return String.format("%s/%s/%s/%s", BuildConfig.IMAGE_URL_BASE, sha.substring(0, 1), sha.substring(0, 2), urlEncode(name));
     }
 
+    /**
+     * Encodes given URL in UTF-8 format
+     * @param url Unformatted URL
+     * @return Formatted URL
+     */
     public static String urlEncode(String url) {
         try {
             return URLEncoder.encode(url, "utf-8");
@@ -61,6 +72,11 @@ public class Utils {
         return string.substring(0, 1).toUpperCase(Locale.getDefault()) + string.substring(1);
     }
 
+    /**
+     * Generates licence name with given ID
+     * @param license License ID
+     * @return Name of license
+     */
     public static int licenseNameFor(String license) {
         switch (license) {
             case Prefs.Licenses.CC_BY_3:
@@ -81,6 +97,12 @@ public class Utils {
         throw new RuntimeException("Unrecognized license value: " + license);
     }
 
+    /**
+     * Fixing incorrect extension
+     * @param title File name
+     * @param extension Correct extension
+     * @return File with correct extension
+     */
     public static String fixExtension(String title, String extension) {
         Pattern jpegPattern = Pattern.compile("\\.jpeg$", Pattern.CASE_INSENSITIVE);
 
@@ -96,6 +118,11 @@ public class Utils {
         return title;
     }
 
+    /**
+     * Tells whether dark theme is active or not
+     * @param context Activity context
+     * @return The state of dark theme
+     */
     public static boolean isDarkTheme(Context context) {
         return PreferenceManager.getDefaultSharedPreferences(context).getBoolean("theme", false);
     }

app/src/main/java/fr/free/nrw/commons/WelcomeActivity.java

@@ -18,6 +18,21 @@ public class WelcomeActivity extends BaseActivity {
 
     private WelcomePagerAdapter adapter = new WelcomePagerAdapter();
 
+    /**
+     * Creates a way to change current activity to WelcomeActivity
+     *
+     * @param context Activity context
+     */
+    public static void startYourself(Context context) {
+        Intent welcomeIntent = new Intent(context, WelcomeActivity.class);
+        context.startActivity(welcomeIntent);
+    }
+
+    /**
+     * Initialises exiting fields and dependencies
+     *
+     * @param savedInstanceState WelcomeActivity bundled data
+     */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -30,14 +45,12 @@ public class WelcomeActivity extends BaseActivity {
         adapter.setCallback(this::finish);
     }
 
+    /**
+     * References WelcomePageAdapter to null before the activity is destroyed
+     */
     @Override
     public void onDestroy() {
         adapter.setCallback(null);
         super.onDestroy();
     }
-
-    public static void startYourself(Context context) {
-        Intent welcomeIntent = new Intent(context, WelcomeActivity.class);
-        context.startActivity(welcomeIntent);
-    }
 }

app/src/main/java/fr/free/nrw/commons/utils/LengthUtils.java

@@ -37,6 +37,13 @@ public class LengthUtils {
         return computeAngleBetween(from, to) * 6371009.0D; // Earth's radius in meter
     }
 
+    /**
+     * Computes angle between two points
+     *
+     * @param from Point A
+     * @param to   Point B
+     * @return Angle in radius
+     */
     private static double computeAngleBetween(LatLng from, LatLng to) {
         return distanceRadians(Math.toRadians(from.getLatitude()),
                 Math.toRadians(from.getLongitude()),
@@ -44,18 +51,43 @@ public class LengthUtils {
                 Math.toRadians(to.getLongitude()));
     }
 
+    /**
+     * Computes arc length between 2 points
+     * @param lat1 Latitude of point A
+     * @param lng1 Longitude of point A
+     * @param lat2 Latitude of point B
+     * @param lng2 Longitude of point B
+     * @return Arc length between the points
+     */
     private static double distanceRadians(double lat1, double lng1, double lat2, double lng2) {
         return arcHav(havDistance(lat1, lat2, lng1 - lng2));
     }
 
+    /**
+     * Gets twice the amount of arc sine of (x)^(1/2)
+     * @param x Angle in radian
+     * @return Twice the angle
+     */
     private static double arcHav(double x) {
         return 2.0D * Math.asin(Math.sqrt(x));
     }
 
+    /**
+     * Computes distance between two points that are on same Longitude
+     * @param lat1 Latitude of point A
+     * @param lat2 Latitude of point B
+     * @param longitude Longitude on which they lie
+     * @return Arc length between points
+     */
     private static double havDistance(double lat1, double lat2, double longitude) {
         return hav(lat1 - lat2) + hav(longitude) * Math.cos(lat1) * Math.cos(lat2);
     }
 
+    /**
+     * Computes square sine function for half of the value entered
+     * @param x Angle in radians
+     * @return One-forth of square of sine function
+     */
     private static double hav(double x) {
         double sinHalf = Math.sin(x * 0.5D);
         return sinHalf * sinHalf;