diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSink.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSink.java
index 22ed3892ec..89de5fb343 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSink.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSink.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.upstream.cache;
 
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.upstream.DataSink;
 import com.google.android.exoplayer2.upstream.DataSpec;
@@ -27,6 +28,7 @@ import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /**
  * Writes data into a cache.
@@ -49,13 +51,13 @@ public final class CacheDataSink implements DataSink {
   private final long fragmentSize;
   private final int bufferSize;
 
-  private DataSpec dataSpec;
+  @Nullable private DataSpec dataSpec;
   private long dataSpecFragmentSize;
-  private File file;
-  private OutputStream outputStream;
+  @Nullable private File file;
+  @Nullable private OutputStream outputStream;
   private long outputStreamBytesWritten;
   private long dataSpecBytesWritten;
-  private ReusableBufferedOutputStream bufferedOutputStream;
+  @MonotonicNonNull private ReusableBufferedOutputStream bufferedOutputStream;
 
   /**
    * Thrown when IOException is encountered when writing data into sink.
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
index 541c3b2d9d..c51f75116f 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
@@ -377,7 +377,7 @@ public final class CacheDataSource implements DataSource {
    *     reading from {@link #upstreamDataSource}, which is the currently open source.
    */
   private void openNextSource(boolean checkCache) throws IOException {
-    CacheSpan nextSpan;
+    @Nullable CacheSpan nextSpan;
     if (currentRequestIgnoresCache) {
       nextSpan = null;
     } else if (blockOnCache) {
@@ -487,7 +487,7 @@ public final class CacheDataSource implements DataSource {
   }
 
   private static Uri getRedirectedUriOrDefault(Cache cache, String key, Uri defaultUri) {
-    Uri redirectedUri = ContentMetadata.getRedirectedUri(cache.getContentMetadata(key));
+    @Nullable Uri redirectedUri = ContentMetadata.getRedirectedUri(cache.getContentMetadata(key));
     return redirectedUri != null ? redirectedUri : defaultUri;
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheFileMetadataIndex.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheFileMetadataIndex.java
index dc27dec363..b2de05ca77 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheFileMetadataIndex.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheFileMetadataIndex.java
@@ -60,7 +60,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
   private final DatabaseProvider databaseProvider;
 
-  private @MonotonicNonNull String tableName;
+  @MonotonicNonNull private String tableName;
 
   /**
    * Deletes index data for the specified cache.
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheKeyFactory.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheKeyFactory.java
index bfa404c074..3401d6f575 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheKeyFactory.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheKeyFactory.java
@@ -24,6 +24,7 @@ public interface CacheKeyFactory {
    * Returns a cache key for the given {@link DataSpec}.
    *
    * @param dataSpec The data being cached.
+   * @return The cache key.
    */
   String buildCacheKey(DataSpec dataSpec);
 }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheUtil.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheUtil.java
index ce16ea2439..fadffd9b95 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheUtil.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheUtil.java
@@ -183,7 +183,7 @@ public final class CacheUtil {
 
     String key = buildCacheKey(dataSpec, cacheKeyFactory);
     long bytesLeft;
-    ProgressNotifier progressNotifier = null;
+    @Nullable ProgressNotifier progressNotifier = null;
     if (progressListener != null) {
       progressNotifier = new ProgressNotifier(progressListener);
       Pair<Long, Long> lengthAndBytesAlreadyCached = getCached(dataSpec, cache, cacheKeyFactory);
@@ -373,7 +373,7 @@ public final class CacheUtil {
   }
 
   /* package */ static boolean isCausedByPositionOutOfRange(IOException e) {
-    Throwable cause = e;
+    @Nullable Throwable cause = e;
     while (cause != null) {
       if (cause instanceof DataSourceException) {
         int reason = ((DataSourceException) cause).reason;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java
index 7e09025ddd..1b9b4a3629 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java
@@ -229,11 +229,12 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
    * @return A new or existing CachedContent instance with the given key.
    */
   public CachedContent getOrAdd(String key) {
-    CachedContent cachedContent = keyToContent.get(key);
+    @Nullable CachedContent cachedContent = keyToContent.get(key);
     return cachedContent == null ? addNew(key) : cachedContent;
   }
 
   /** Returns a CachedContent instance with the given key or null if there isn't one. */
+  @Nullable
   public CachedContent get(String key) {
     return keyToContent.get(key);
   }
@@ -254,14 +255,15 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
     return getOrAdd(key).id;
   }
 
-  /** Returns the key which has the given id assigned. */
+  /** Returns the key which has the given id assigned, or {@code null} if no such key exists. */
+  @Nullable
   public String getKeyForId(int id) {
     return idToKey.get(id);
   }
 
   /** Removes {@link CachedContent} with the given key from index if it's empty and not locked. */
   public void maybeRemove(String key) {
-    CachedContent cachedContent = keyToContent.get(key);
+    @Nullable CachedContent cachedContent = keyToContent.get(key);
     if (cachedContent != null && cachedContent.isEmpty() && !cachedContent.isLocked()) {
       keyToContent.remove(key);
       int id = cachedContent.id;
@@ -626,7 +628,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
     }
 
     private void writeFile(HashMap<String, CachedContent> content) throws IOException {
-      DataOutputStream output = null;
+      @Nullable DataOutputStream output = null;
       try {
         OutputStream outputStream = atomicFile.startWrite();
         if (bufferedOutputStream == null) {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java
index fb2d4f694f..15a827ba74 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java
@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.upstream.cache;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.extractor.ChunkIndex;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
@@ -77,7 +78,7 @@ public final class CachedRegionTracker implements Cache.Listener {
    */
   public synchronized int getRegionEndTimeMs(long byteOffset) {
     lookupRegion.startOffset = byteOffset;
-    Region floorRegion = regions.floor(lookupRegion);
+    @Nullable Region floorRegion = regions.floor(lookupRegion);
     if (floorRegion == null || byteOffset > floorRegion.endOffset
         || floorRegion.endOffsetIndex == -1) {
       return NOT_CACHED;
@@ -102,7 +103,7 @@ public final class CachedRegionTracker implements Cache.Listener {
     Region removedRegion = new Region(span.position, span.position + span.length);
 
     // Look up a region this span falls into.
-    Region floorRegion = regions.floor(removedRegion);
+    @Nullable Region floorRegion = regions.floor(removedRegion);
     if (floorRegion == null) {
       Log.e(TAG, "Removed a span we were not aware of");
       return;
@@ -134,8 +135,8 @@ public final class CachedRegionTracker implements Cache.Listener {
 
   private void mergeSpan(CacheSpan span) {
     Region newRegion = new Region(span.position, span.position + span.length);
-    Region floorRegion = regions.floor(newRegion);
-    Region ceilingRegion = regions.ceiling(newRegion);
+    @Nullable Region floorRegion = regions.floor(newRegion);
+    @Nullable Region ceilingRegion = regions.ceiling(newRegion);
     boolean floorConnects = regionsConnect(floorRegion, newRegion);
     boolean ceilingConnects = regionsConnect(newRegion, ceilingRegion);
 
@@ -168,7 +169,7 @@ public final class CachedRegionTracker implements Cache.Listener {
     }
   }
 
-  private boolean regionsConnect(Region lower, Region upper) {
+  private boolean regionsConnect(@Nullable Region lower, @Nullable Region upper) {
     return lower != null && upper != null && lower.endOffset == upper.startOffset;
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadata.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadata.java
index 4cc6e6b860..26b6d83a43 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadata.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadata.java
@@ -81,7 +81,7 @@ public interface ContentMetadata {
    */
   @Nullable
   static Uri getRedirectedUri(ContentMetadata contentMetadata) {
-    String redirectedUri = contentMetadata.get(KEY_REDIRECTED_URI, (String) null);
+    @Nullable String redirectedUri = contentMetadata.get(KEY_REDIRECTED_URI, (String) null);
     return redirectedUri == null ? null : Uri.parse(redirectedUri);
   }
 }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadataMutations.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadataMutations.java
index 5715b8fbd4..f6cac58997 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadataMutations.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadataMutations.java
@@ -73,8 +73,7 @@ public class ContentMetadataMutations {
   }
 
   /**
-   * Adds a mutation to set a metadata value. Passing {@code null} as {@code name} or {@code value}
-   * isn't allowed.
+   * Adds a mutation to set a metadata value.
    *
    * @param name The name of the metadata value.
    * @param value The value to be set.
@@ -85,7 +84,7 @@ public class ContentMetadataMutations {
   }
 
   /**
-   * Adds a mutation to set a metadata value. Passing {@code null} as {@code name} isn't allowed.
+   * Adds a mutation to set a metadata value.
    *
    * @param name The name of the metadata value.
    * @param value The value to be set.
@@ -96,8 +95,7 @@ public class ContentMetadataMutations {
   }
 
   /**
-   * Adds a mutation to set a metadata value. Passing {@code null} as {@code name} or {@code value}
-   * isn't allowed.
+   * Adds a mutation to set a metadata value.
    *
    * @param name The name of the metadata value.
    * @param value The value to be set.
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadata.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadata.java
index 1f07af938a..c3f06252e4 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadata.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadata.java
@@ -67,8 +67,8 @@ public final class DefaultContentMetadata implements ContentMetadata {
   @Override
   @Nullable
   public final byte[] get(String name, @Nullable byte[] defaultValue) {
-    if (metadata.containsKey(name)) {
-      byte[] bytes = metadata.get(name);
+    @Nullable byte[] bytes = metadata.get(name);
+    if (bytes != null) {
       return Arrays.copyOf(bytes, bytes.length);
     } else {
       return defaultValue;
@@ -78,8 +78,8 @@ public final class DefaultContentMetadata implements ContentMetadata {
   @Override
   @Nullable
   public final String get(String name, @Nullable String defaultValue) {
-    if (metadata.containsKey(name)) {
-      byte[] bytes = metadata.get(name);
+    @Nullable byte[] bytes = metadata.get(name);
+    if (bytes != null) {
       return new String(bytes, Charset.forName(C.UTF8_NAME));
     } else {
       return defaultValue;
@@ -88,8 +88,8 @@ public final class DefaultContentMetadata implements ContentMetadata {
 
   @Override
   public final long get(String name, long defaultValue) {
-    if (metadata.containsKey(name)) {
-      byte[] bytes = metadata.get(name);
+    @Nullable byte[] bytes = metadata.get(name);
+    if (bytes != null) {
       return ByteBuffer.wrap(bytes).getLong();
     } else {
       return defaultValue;
@@ -130,7 +130,7 @@ public final class DefaultContentMetadata implements ContentMetadata {
     }
     for (Entry<String, byte[]> entry : first.entrySet()) {
       byte[] value = entry.getValue();
-      byte[] otherValue = second.get(entry.getKey());
+      @Nullable byte[] otherValue = second.get(entry.getKey());
       if (!Arrays.equals(value, otherValue)) {
         return false;
       }
@@ -153,8 +153,8 @@ public final class DefaultContentMetadata implements ContentMetadata {
   }
 
   private static void addValues(HashMap<String, byte[]> metadata, Map<String, Object> values) {
-    for (String name : values.keySet()) {
-      metadata.put(name, getBytes(values.get(name)));
+    for (Entry<String, Object> entry : values.entrySet()) {
+      metadata.put(entry.getKey(), getBytes(entry.getValue()));
     }
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
index a4fade25e0..5f420c3197 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
@@ -465,8 +465,7 @@ public final class SimpleCache implements Cache {
   @Override
   public synchronized void releaseHoleSpan(CacheSpan holeSpan) {
     Assertions.checkState(!released);
-    CachedContent cachedContent = contentIndex.get(holeSpan.key);
-    Assertions.checkNotNull(cachedContent);
+    CachedContent cachedContent = Assertions.checkNotNull(contentIndex.get(holeSpan.key));
     Assertions.checkState(cachedContent.isLocked());
     cachedContent.setLocked(false);
     contentIndex.maybeRemove(cachedContent.key);
@@ -482,14 +481,14 @@ public final class SimpleCache implements Cache {
   @Override
   public synchronized boolean isCached(String key, long position, long length) {
     Assertions.checkState(!released);
-    CachedContent cachedContent = contentIndex.get(key);
+    @Nullable CachedContent cachedContent = contentIndex.get(key);
     return cachedContent != null && cachedContent.getCachedBytesLength(position, length) >= length;
   }
 
   @Override
   public synchronized long getCachedLength(String key, long position, long length) {
     Assertions.checkState(!released);
-    CachedContent cachedContent = contentIndex.get(key);
+    @Nullable CachedContent cachedContent = contentIndex.get(key);
     return cachedContent != null ? cachedContent.getCachedBytesLength(position, length) : -length;
   }
 
@@ -524,7 +523,7 @@ public final class SimpleCache implements Cache {
       }
     }
 
-    File[] files = cacheDir.listFiles();
+    @Nullable File[] files = cacheDir.listFiles();
     if (files == null) {
       String message = "Failed to list cache directory files: " + cacheDir;
       Log.e(TAG, message);
@@ -605,11 +604,13 @@ public final class SimpleCache implements Cache {
         }
         long length = C.LENGTH_UNSET;
         long lastTouchTimestamp = C.TIME_UNSET;
+        @Nullable
         CacheFileMetadata metadata = fileMetadata != null ? fileMetadata.remove(fileName) : null;
         if (metadata != null) {
           length = metadata.length;
           lastTouchTimestamp = metadata.lastTouchTimestamp;
         }
+        @Nullable
         SimpleCacheSpan span =
             SimpleCacheSpan.createCacheEntry(file, length, lastTouchTimestamp, contentIndex);
         if (span != null) {
@@ -666,7 +667,7 @@ public final class SimpleCache implements Cache {
    * @return The corresponding cache {@link SimpleCacheSpan}.
    */
   private SimpleCacheSpan getSpan(String key, long position) {
-    CachedContent cachedContent = contentIndex.get(key);
+    @Nullable CachedContent cachedContent = contentIndex.get(key);
     if (cachedContent == null) {
       return SimpleCacheSpan.createOpenHole(key, position);
     }
@@ -694,7 +695,7 @@ public final class SimpleCache implements Cache {
   }
 
   private void removeSpanInternal(CacheSpan span) {
-    CachedContent cachedContent = contentIndex.get(span.key);
+    @Nullable CachedContent cachedContent = contentIndex.get(span.key);
     if (cachedContent == null || !cachedContent.removeSpan(span)) {
       return;
     }
@@ -732,7 +733,7 @@ public final class SimpleCache implements Cache {
   }
 
   private void notifySpanRemoved(CacheSpan span) {
-    ArrayList<Listener> keyListeners = listeners.get(span.key);
+    @Nullable ArrayList<Listener> keyListeners = listeners.get(span.key);
     if (keyListeners != null) {
       for (int i = keyListeners.size() - 1; i >= 0; i--) {
         keyListeners.get(i).onSpanRemoved(this, span);
@@ -742,7 +743,7 @@ public final class SimpleCache implements Cache {
   }
 
   private void notifySpanAdded(SimpleCacheSpan span) {
-    ArrayList<Listener> keyListeners = listeners.get(span.key);
+    @Nullable ArrayList<Listener> keyListeners = listeners.get(span.key);
     if (keyListeners != null) {
       for (int i = keyListeners.size() - 1; i >= 0; i--) {
         keyListeners.get(i).onSpanAdded(this, span);
@@ -752,7 +753,7 @@ public final class SimpleCache implements Cache {
   }
 
   private void notifySpanTouched(SimpleCacheSpan oldSpan, CacheSpan newSpan) {
-    ArrayList<Listener> keyListeners = listeners.get(oldSpan.key);
+    @Nullable ArrayList<Listener> keyListeners = listeners.get(oldSpan.key);
     if (keyListeners != null) {
       for (int i = keyListeners.size() - 1; i >= 0; i--) {
         keyListeners.get(i).onSpanTouched(this, oldSpan, newSpan);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheSpan.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheSpan.java
index 5f6ea338e6..ce195baf4e 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheSpan.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCacheSpan.java
@@ -91,6 +91,7 @@ import java.util.regex.Pattern;
    * @param length The length of the cache file in bytes, or {@link C#LENGTH_UNSET} to query the
    *     underlying file system. Querying the underlying file system can be expensive, so callers
    *     that already know the length of the file should pass it explicitly.
+   * @param index The cached content index.
    * @return The span, or null if the file name is not correctly formatted, or if the id is not
    *     present in the content index, or if the length is 0.
    */
@@ -108,6 +109,7 @@ import java.util.regex.Pattern;
    *     that already know the length of the file should pass it explicitly.
    * @param lastTouchTimestamp The last touch timestamp, or {@link C#TIME_UNSET} to use the file
    *     timestamp.
+   * @param index The cached content index.
    * @return The span, or null if the file name is not correctly formatted, or if the id is not
    *     present in the content index, or if the length is 0.
    */
@@ -130,7 +132,7 @@ import java.util.regex.Pattern;
     }
 
     int id = Integer.parseInt(matcher.group(1));
-    String key = index.getKeyForId(id);
+    @Nullable String key = index.getKeyForId(id);
     if (key == null) {
       return null;
     }
@@ -153,26 +155,26 @@ import java.util.regex.Pattern;
    * Upgrades the cache file if it is created by an earlier version of {@link SimpleCache}.
    *
    * @param file The cache file.
-   * @param index Cached content index.
+   * @param index The cached content index.
    * @return Upgraded cache file or {@code null} if the file name is not correctly formatted or the
    *     file can not be renamed.
    */
   @Nullable
   private static File upgradeFile(File file, CachedContentIndex index) {
-    String key;
+    @Nullable String key = null;
     String filename = file.getName();
     Matcher matcher = CACHE_FILE_PATTERN_V2.matcher(filename);
     if (matcher.matches()) {
       key = Util.unescapeFileName(matcher.group(1));
-      if (key == null) {
-        return null;
-      }
     } else {
       matcher = CACHE_FILE_PATTERN_V1.matcher(filename);
-      if (!matcher.matches()) {
-        return null;
+      if (matcher.matches()) {
+        key = matcher.group(1); // Keys were not escaped in version 1.
       }
-      key = matcher.group(1); // Keys were not escaped in version 1.
+    }
+
+    if (key == null) {
+      return null;
     }
 
     File newCacheFile =
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/package-info.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/package-info.java
new file mode 100644
index 0000000000..bb6cf77458
--- /dev/null
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/package-info.java
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.upstream.cache;
+
+import com.google.android.exoplayer2.util.NonNullApi;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/package-info.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/package-info.java
new file mode 100644
index 0000000000..9c4005e815
--- /dev/null
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/package-info.java
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.upstream.crypto;
+
+import com.google.android.exoplayer2.util.NonNullApi;