Remove null-ness of muxedCaptionFormats list

Pre-work for removing HlsMasterPlaylist and HlsPlaylistParser from null-checking
blacklist.

PiperOrigin-RevId: 274585117

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java

@@ -635,10 +635,8 @@ public final class HlsMediaPeriod implements MediaPeriod, HlsSampleStreamWrapper
                       /* isPrimaryTrackInVariant= */ false)));
         }
         List<Format> ccFormats = masterPlaylist.muxedCaptionFormats;
-        if (ccFormats != null) {
+        for (int i = 0; i < ccFormats.size(); i++) {
-          for (int i = 0; i < ccFormats.size(); i++) {
+          muxedTrackGroups.add(new TrackGroup(ccFormats.get(i)));
-            muxedTrackGroups.add(new TrackGroup(ccFormats.get(i)));
-          }
         }
       } else if (variantsContainAudioCodecs) {
         // Variants only contain audio.

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsMasterPlaylist.java

@@ -177,8 +177,7 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
   @Nullable public final Format muxedAudioFormat;
   /**
    * The format of the closed captions declared by the playlist. May be empty if the playlist
-   * explicitly declares no captions are available, or null if the playlist does not declare any
+   * doesn't declare any caption information or explicitly declares no captions are available.
-   * captions information.
    */
   public final List<Format> muxedCaptionFormats;
   /** Contains variable definitions, as defined by the #EXT-X-DEFINE tag. */
@@ -223,8 +222,7 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
     this.subtitles = Collections.unmodifiableList(subtitles);
     this.closedCaptions = Collections.unmodifiableList(closedCaptions);
     this.muxedAudioFormat = muxedAudioFormat;
-    this.muxedCaptionFormats = muxedCaptionFormats != null
+    this.muxedCaptionFormats = Collections.unmodifiableList(muxedCaptionFormats);
-        ? Collections.unmodifiableList(muxedCaptionFormats) : null;
     this.variableDefinitions = Collections.unmodifiableMap(variableDefinitions);
     this.sessionKeyDrmInitData = Collections.unmodifiableList(sessionKeyDrmInitData);
   }
@@ -266,7 +264,7 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
         /* subtitles= */ Collections.emptyList(),
         /* closedCaptions= */ Collections.emptyList(),
         /* muxedAudioFormat= */ null,
-        /* muxedCaptionFormats= */ null,
+        /* muxedCaptionFormats= */ Collections.emptyList(),
         /* hasIndependentSegments= */ false,
         /* variableDefinitions= */ Collections.emptyMap(),
         /* sessionKeyDrmInitData= */ Collections.emptyList());

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistParser.java

@@ -267,7 +267,7 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
     ArrayList<DrmInitData> sessionKeyDrmInitData = new ArrayList<>();
     ArrayList<String> tags = new ArrayList<>();
     Format muxedAudioFormat = null;
-    List<Format> muxedCaptionFormats = null;
+    List<Format> muxedCaptionFormats = new ArrayList<>();
     boolean noClosedCaptions = false;
     boolean hasIndependentSegmentsTag = false;
 
@@ -494,9 +494,6 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
             mimeType = MimeTypes.APPLICATION_CEA708;
             accessibilityChannel = Integer.parseInt(instreamId.substring(7));
           }
-          if (muxedCaptionFormats == null) {
-            muxedCaptionFormats = new ArrayList<>();
-          }
           muxedCaptionFormats.add(
               Format.createTextContainerFormat(
                   /* id= */ formatId,
@@ -518,7 +515,7 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
     }
 
     if (noClosedCaptions) {
-      muxedCaptionFormats = Collections.emptyList();
+      muxedCaptionFormats.clear();
     }
 
     return new HlsMasterPlaylist(

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/HlsMasterPlaylistParserTest.java

@@ -200,7 +200,7 @@ public class HlsMasterPlaylistParserTest {
 
     List<HlsMasterPlaylist.Variant> variants = masterPlaylist.variants;
     assertThat(variants).hasSize(5);
-    assertThat(masterPlaylist.muxedCaptionFormats).isNull();
+    assertThat(masterPlaylist.muxedCaptionFormats).isEmpty();
 
     assertThat(variants.get(0).format.bitrate).isEqualTo(1280000);
     assertThat(variants.get(0).format.codecs).isEqualTo("mp4a.40.2,avc1.66.30");

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/HlsMediaPlaylistParserTest.java

@@ -456,7 +456,7 @@ public class HlsMediaPlaylistParserTest {
             /* subtitles= */ Collections.emptyList(),
             /* closedCaptions= */ Collections.emptyList(),
             /* muxedAudioFormat= */ null,
-            /* muxedCaptionFormats= */ null,
+            /* muxedCaptionFormats= */ Collections.emptyList(),
             /* hasIndependentSegments= */ true,
             /* variableDefinitions= */ Collections.emptyMap(),
             /* sessionKeyDrmInitData= */ Collections.emptyList());