Code optimization. Added javadoc. Removed setSize for it is not used

Fixed some mistakes.

Code optimization. Added comments. Few comment mistake fixes

Few comments

Added classes because of renaming

Fixed refactor mistakes :(.

typo + removed todo empty class

Changed o to 0. Some renaming.  Checked for nullability on string.isEmpty() function to prevent crashes

Removed redundant null check

Update ChapterCache.java

Another o to 0 change. Damn this .o! :)

app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsAdvancedFragment.java

@@ -71,7 +71,7 @@ public class SettingsAdvancedFragment extends SettingsNestedFragment {
 
         subscriptions.add(Observable.defer(() -> Observable.from(files))
                 .concatMap(file -> {
-                    if (chapterCache.remove(file.getName())) {
+                    if (chapterCache.removeFileFromCache(file.getName())) {
                         deletedFiles.incrementAndGet();
                     }
                     return Observable.just(file);