Summary

Change java.nio.channels.FileChannel::transferFrom to extend the channel's file if position > size() instead of writing no bytes.

Problem

Currently passing a position value which is greater than FileChannel::size to FileChannel::transferFrom results in no bytes being written. This is inconsistent with FileChannel::write(ByteBuffer,long) which extends the channel's file if position > size().

Solution

Modify FileChannel::transferFrom to extend the channel's file when position > size() in the same manner as the positional FileChannel:write.

Specification

    --- a/src/java.base/share/classes/java/nio/channels/FileChannel.java
    +++ b/src/java.base/share/classes/java/nio/channels/FileChannel.java
    @@ -701,8 +701,10 @@ public abstract class FileChannel
      * source has reached end-of-stream.
      *
      * <p> This method does not modify this channel's position.  If the given
-     * position is greater than the file's current size then no bytes are
-     * transferred.  If the source channel has a position then bytes are read
+     * position is greater than or equal to the file's current size then the
+     * file will be grown to accommodate the new bytes; the values of any bytes
+     * between the previous end-of-file and the newly-written bytes are
+     * unspecified.  If the source channel has a position then bytes are read
      * starting at that position and then the position is incremented by the
      * number of bytes read.
      *