Refactor Extractor

- Renaming and removal of duplicate code
- New base class for list extractors

ListExtractor.java

@@ -0,0 +1,32 @@
+package org.schabi.newpipe.extractor;
+
+import org.schabi.newpipe.extractor.exceptions.ExtractionException;
+import org.schabi.newpipe.extractor.stream.StreamInfoItemCollector;
+
+import java.io.IOException;
+
+/**
+ * Base class to extractors that have a list (e.g. playlists, channels).
+ */
+public abstract class ListExtractor extends Extractor {
+    protected String nextStreamsUrl;
+
+    public ListExtractor(UrlIdHandler urlIdHandler, int serviceId, String url) {
+        super(urlIdHandler, serviceId, url);
+    }
+
+    public boolean hasMoreStreams(){
+        return nextStreamsUrl != null && !nextStreamsUrl.isEmpty();
+    }
+
+    public abstract StreamInfoItemCollector getNextStreams() throws ExtractionException, IOException;
+
+    public String getNextStreamsUrl() {
+        return nextStreamsUrl;
+    }
+
+    public void setNextStreamsUrl(String nextStreamsUrl) {
+        this.nextStreamsUrl = nextStreamsUrl;
+    }
+
+}

StreamingService.java

@@ -27,14 +27,15 @@ public abstract class StreamingService {
     }
 
     public abstract ServiceInfo getServiceInfo();
-    public abstract StreamExtractor getExtractorInstance(String url) throws IOException, ExtractionException;
+
-    public abstract SearchEngine getSearchEngineInstance();
     public abstract UrlIdHandler getStreamUrlIdHandlerInstance();
     public abstract UrlIdHandler getChannelUrlIdHandlerInstance();
     public abstract UrlIdHandler getPlaylistUrlIdHandlerInstance();
+    public abstract SearchEngine getSearchEngineInstance();
+    public abstract SuggestionExtractor getSuggestionExtractorInstance();
+    public abstract StreamExtractor getStreamExtractorInstance(String url) throws IOException, ExtractionException;
     public abstract ChannelExtractor getChannelExtractorInstance(String url) throws ExtractionException, IOException;
     public abstract PlaylistExtractor getPlaylistExtractorInstance(String url) throws ExtractionException, IOException;
-    public abstract SuggestionExtractor getSuggestionExtractorInstance();
 
 
     public final int getServiceId() {

channel/ChannelExtractor.java

@@ -1,6 +1,7 @@
 package org.schabi.newpipe.extractor.channel;
 
 import org.schabi.newpipe.extractor.Extractor;
+import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.UrlIdHandler;
 import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
@@ -28,7 +29,7 @@ import java.io.IOException;
  * along with NewPipe.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-public abstract class ChannelExtractor extends Extractor {
+public abstract class ChannelExtractor extends ListExtractor {
 
     public ChannelExtractor(UrlIdHandler urlIdHandler, String url, int serviceId) throws ExtractionException, IOException {
         super(urlIdHandler, serviceId, url);
@@ -41,7 +42,5 @@ public abstract class ChannelExtractor extends Extractor {
     public abstract String getFeedUrl() throws ParsingException;
     public abstract StreamInfoItemCollector getStreams() throws ParsingException;
     public abstract long getSubscriberCount() throws ParsingException;
-    public abstract boolean hasMoreStreams();
-    public abstract StreamInfoItemCollector getNextStreams() throws ExtractionException, IOException;
 
 }

playlist/PlaylistExtractor.java

@@ -1,6 +1,7 @@
 package org.schabi.newpipe.extractor.playlist;
 
 import org.schabi.newpipe.extractor.Extractor;
+import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.UrlIdHandler;
 import org.schabi.newpipe.extractor.exceptions.ExtractionException;
 import org.schabi.newpipe.extractor.exceptions.ParsingException;
@@ -8,7 +9,7 @@ import org.schabi.newpipe.extractor.stream.StreamInfoItemCollector;
 
 import java.io.IOException;
 
-public abstract class PlaylistExtractor extends Extractor {
+public abstract class PlaylistExtractor extends ListExtractor {
 
     public PlaylistExtractor(UrlIdHandler urlIdHandler, String url, int serviceId) throws ExtractionException, IOException {
         super(urlIdHandler, serviceId, url);
@@ -23,7 +24,4 @@ public abstract class PlaylistExtractor extends Extractor {
     public abstract String getUploaderAvatarUrl() throws ParsingException;
     public abstract StreamInfoItemCollector getStreams() throws ParsingException;
     public abstract long getStreamsCount() throws ParsingException;
-    public abstract boolean hasMoreStreams();
-    public abstract StreamInfoItemCollector getNextStreams() throws ExtractionException, IOException;
-
 }

services/youtube/YoutubeChannelExtractor.java

@@ -49,7 +49,6 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
      * It's lazily initialized (when getNextStreams is called)
      */
     private Document nextStreamsAjax;
-    private String nextStreamsUrl = "";
 
     /*//////////////////////////////////////////////////////////////////////////
     // Variables for cache purposes (not "select" the current document all over again)
@@ -61,7 +60,6 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
     private String feedUrl;
     private long subscriberCount = -1;
 
-
     public YoutubeChannelExtractor(UrlIdHandler urlIdHandler, String url, int serviceId) throws ExtractionException, IOException {
         super(urlIdHandler, urlIdHandler.cleanUrl(url), serviceId);
         fetchDocument();
@@ -160,14 +158,11 @@ public class YoutubeChannelExtractor extends ChannelExtractor {
         }
     }
 
-    @Override
-    public boolean hasMoreStreams() {
-        return nextStreamsUrl != null && !nextStreamsUrl.isEmpty();
-    }
-
     @Override
     public StreamInfoItemCollector getNextStreams() throws ExtractionException, IOException {
-        if (!hasMoreStreams()) throw new ExtractionException("Channel doesn't have more streams");
+        if (!hasMoreStreams()) {
+            throw new ExtractionException("Channel doesn't have more streams");
+        }
 
         StreamInfoItemCollector collector = new StreamInfoItemCollector(getUrlIdHandler(), getServiceId());
         setupNextStreamsAjax(NewPipe.getDownloader());

services/youtube/YoutubePlaylistExtractor.java

@@ -27,7 +27,6 @@ public class YoutubePlaylistExtractor extends PlaylistExtractor {
      * It's lazily initialized (when getNextStreams is called)
      */
     private Document nextStreamsAjax = null;
-    private String nextStreamsUrl = "";
 
     /*//////////////////////////////////////////////////////////////////////////
     // Variables for cache purposes (not "select" the current document all over again)
@@ -181,14 +180,11 @@ public class YoutubePlaylistExtractor extends PlaylistExtractor {
         return collector;
     }
 
-    @Override
-    public boolean hasMoreStreams() {
-        return nextStreamsUrl != null && !nextStreamsUrl.isEmpty();
-    }
-
     @Override
     public StreamInfoItemCollector getNextStreams() throws ExtractionException, IOException {
-        if (!hasMoreStreams()) throw new ExtractionException("Playlist doesn't have more streams");
+        if (!hasMoreStreams()){
+            throw new ExtractionException("Playlist doesn't have more streams");
+        }
 
         StreamInfoItemCollector collector = new StreamInfoItemCollector(getUrlIdHandler(), getServiceId());
         setupNextStreamsAjax(NewPipe.getDownloader());

services/youtube/YoutubeService.java

@@ -46,7 +46,7 @@ public class YoutubeService extends StreamingService {
     }
 
     @Override
-    public StreamExtractor getExtractorInstance(String url)
+    public StreamExtractor getStreamExtractorInstance(String url)
             throws ExtractionException, IOException {
         UrlIdHandler urlIdHandler = YoutubeStreamUrlIdHandler.getInstance();
         if (urlIdHandler.acceptUrl(url)) {