Seeking a ByteArrayInputStream using java.io

How can I seek (change the position) of a ByteArrayInputStream (java.io)? It is something so obvious, but I can't seem to find a method for this anywhere (mark/reset is not enough, I need to set the position to anywhere on the InputStream).

If it can't be done using java.io and I must switch to java.nio and use a ByteBuffer, how can I get something similar to a DataOutputStream wrapping a ByteArrayOutputStream using java.nio? I'm not finding any kind of auto-resizable buffer.

EDIT: I've found one way to achieve what I'm attempting to do, but it's a bit messy. ImageIO.createImageInputStream creates a ImageInputStream, which is exactly what I want (can seek and read primitives). However, using a ByteArrayInputStream returns a FileCacheImageInputStream, which basically means it copies the byte array to a file just to seek.

This is my first time trying to use the Java IO class开发者_如何学运维es and it has been completely negative. It's missing some fundamental (IMO) features, and it has lots of ways to do the same thing (e.g. to read primitives from a file you can either use RandomAccessFile, DataInputStream + FileInputStream, FileImageInputStream, FileChannel + ByteBuffer, and maybe even more).

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You'd use reset()/skip(). I can't say it's the nicest API in the world, but it should work:

public void seek(ByteArrayInputStream input, int position)
    throws IOException
{
    input.reset();
    input.skip(position);
}

Of course, that assumes that no-one has called mark().

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If you are creating the ByteArrayInputStream to pass elsewhere, extend the class and manipulate pos (a protected member of ByteArrayInputStream) as you wish.

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There is a ByteArrayInputStream(byte(), int, int) constructor that will give you an input stream that will read up to a given count of bytes starting from a given offset. You can use this to simulate seeking to an arbitrary offset in the stream.

You have to deal with the fact that "seeking" gives you a new stream object, and this may be awkward. However, this approach does not involve copying any bytes or saving them to a file, and it should be safe to not bother with closing the ByteArrayInputStream objects.