Most efficient way to create InputStream from OutputStream

Question

This page: http://blog.ostermiller.org/convert-java-outputstream-inputstream describes how to create an InputStream from OutputStream:

new ByteArrayInputStr         


        

Answer 1

I usually try to avoid creating a separate thread because of the increased chance of deadlock, the increased difficulty of understanding the code, and the problems of dealing with exceptions.

Here's my proposed solution: a ProducerInputStream that creates content in chunks by repeated calls to produceChunk():

public abstract class ProducerInputStream extends InputStream {

    private ByteArrayInputStream bin = new ByteArrayInputStream(new byte[0]);
    private ByteArrayOutputStream bout = new ByteArrayOutputStream();

    @Override
    public int read() throws IOException {
        int result = bin.read();
        while ((result == -1) && newChunk()) {
            result = bin.read();
        }
        return result;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        int result = bin.read(b, off, len);
        while ((result == -1) && newChunk()) {
            result = bin.read(b, off, len);
        }
        return result;
    }

    private boolean newChunk() {
        bout.reset();
        produceChunk(bout);
        bin = new ByteArrayInputStream(bout.toByteArray());
        return (bout.size() > 0);
    }

    public abstract void produceChunk(OutputStream out);

}