Give constant -1 different names.

core/client/fs/src/main/java/alluxio/client/file/FileInStream.java

@@ -61,6 +61,9 @@ public class FileInStream extends InputStream
 
   private static final boolean PASSIVE_CACHE_ENABLED =
       Configuration.getBoolean(PropertyKey.USER_FILE_PASSIVE_CACHE_ENABLED);
+  private static final int UNINITIALIZED_BLOCK_INDEX = -1;
+  private static final int EOF_DATA = -1;
+  private static final int EOF_BLOCK_ID = -1;
 
   /** The instream options. */
   private final InStreamOptions mInStreamOptions;
@@ -105,7 +108,7 @@ public class FileInStream extends InputStream
    * current block stream yet. When the file stream has reached EOF, it is set to the length of
    * {@link #mBlockIds}.
    */
-  private int mBlockIdIndex = -1;
+  private int mBlockIndex = UNINITIALIZED_BLOCK_INDEX;
 
   /** The read buffer in file seek. This is used in {@link #readCurrentBlockToEnd()}. */
   private final byte[] mSeekBuffer;
@@ -196,15 +199,15 @@ public int read(byte[] b, int off, int len) throws IOException {
 
   private int readInternal() throws IOException {
     if (remainingInternal() <= 0) {
-      return -1;
+      return EOF_BLOCK_ID;
     }
     updateStreams();
     Preconditions.checkState(mCurrentBlockInStream != null, PreconditionMessage.ERR_UNEXPECTED_EOF);
 
     int data = mCurrentBlockInStream.read();
-    if (data == -1) {
+    if (data == EOF_DATA) {
       // The underlying stream is done.
-      return -1;
+      return EOF_DATA;
     }
 
     mPos++;
@@ -225,7 +228,7 @@ private int readInternal(byte[] b, int off, int len) throws IOException {
     if (len == 0) {
       return 0;
     } else if (remainingInternal() <= 0) {
-      return -1;
+      return EOF_DATA;
     }
 
     int currentOffset = off;
@@ -258,7 +261,7 @@ private int readInternal(byte[] b, int off, int len) throws IOException {
 
     if (bytesLeftToRead == len && mCurrentBlockInStream.remaining() == 0) {
       // Nothing was read, and the underlying stream is done.
-      return -1;
+      return EOF_DATA;
     }
 
     return len - bytesLeftToRead;
@@ -271,7 +274,7 @@ public int positionedRead(long pos, byte[] b, int off, int len) throws IOExcepti
 
   private int positionedReadInternal(long pos, byte[] b, int off, int len) throws IOException {
     if (pos < 0 || pos >= mFileLength) {
-      return -1;
+      return EOF_DATA;
     }
 
     // If partial read cache is enabled, we fall back to the normal read.
@@ -387,7 +390,7 @@ protected long getBlockSize(long pos) {
    * @return true if the block stream should be updated
    */
   protected boolean shouldUpdateStreams() {
-    if (mBlockIdIndex == mBlockIds.size()) {
+    if (mBlockIndex == mBlockIds.size()) {
       // EOF.
       return false;
     }
@@ -437,15 +440,15 @@ private void closeOrCancelCacheStream() {
   }
 
   /**
-   * @return the current block id based on mBlockIdIndex, -1 if at the end of the file
+   * @return the current block id based on mBlockIndex, -1 if at the end of the file
    */
   private long getCurrentBlockId() {
     if (remainingInternal() <= 0) {
-      return -1;
+      return EOF_BLOCK_ID;
     }
-    Preconditions.checkState(mBlockIdIndex < mBlockIds.size(),
-        PreconditionMessage.ERR_BLOCK_INDEX.toString(), mBlockIdIndex, mPos, mBlockIds.size() - 1);
-    return mBlockIds.get(mBlockIdIndex);
+    Preconditions.checkState(mBlockIndex < mBlockIds.size(),
+        PreconditionMessage.ERR_BLOCK_INDEX.toString(), mBlockIndex, mPos, mBlockIds.size() - 1);
+    return mBlockIds.get(mBlockIndex);
   }
 
   /**
@@ -481,30 +484,34 @@ private void handleCacheStreamException(IOException e) {
 
   /**
    * Checks whether the current block stream has remaining bytes, if not, advance to the next block
-   * stream, otherwise, this is a no-op. This should only be used in streaming read APIs.
-   * For APIs like {@link #seek(long)}, {@link #skip(long)}, the block stream should be updated
-   * according to the current read position, use {@link #updateStreamsBasedOnPosition()} instead.
+   * stream, otherwise, this is a no-op.
+   *
+   * This should only be used in streaming read APIs. For APIs like {@link #seek(long)},
+   * {@link #skip(long)}, the block stream should be updated according to the current read position,
+   * use {@link #updateStreamsBasedOnPosition()} instead.
    */
   private void updateStreams() throws IOException {
     assureCacheStreamInSync();
     if (shouldUpdateStreams()) {
-      mBlockIdIndex++;
+      mBlockIndex++;
       updateStreamsInternal();
     }
   }
 
   /**
    * Computes the current block stream ID based on the current read position, if the stream ID is
-   * different from the current block stream ID, then updates the stream.
+   * different from the current block stream ID, or the stream ID is the same as the current
+   * block stream ID but the current stream has no remaining bytes, then updates the stream.
+   *
    * Comparing to {@link #updateStreams()}, this method has overhead for computing the
    * block stream ID, only use this method for non-streaming read APIs like {@link #seek(long)}
    * and {@link #skip(long)}.
    */
   private void updateStreamsBasedOnPosition() throws IOException {
     assureCacheStreamInSync();
-    int blockIdIndex = (int) (mPos / mBlockSize);
-    if (blockIdIndex != mBlockIdIndex || shouldUpdateStreams()) {
-      mBlockIdIndex = blockIdIndex;
+    int blockIndex = (int) (mPos / mBlockSize);
+    if (blockIndex != mBlockIndex || shouldUpdateStreams()) {
+      mBlockIndex = blockIndex;
       updateStreamsInternal();
     }
   }
@@ -589,8 +596,7 @@ private void updateBlockInStream(long blockId) throws IOException {
       mCurrentBlockInStream = null;
     }
 
-    // blockId = -1 if mPos = EOF.
-    if (blockId < 0) {
+    if (blockId == EOF_BLOCK_ID) {
       return;
     }
     mCurrentBlockInStream = getBlockInStream(blockId);