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

A simple solution that avoids copying the buffer is to create a special-purpose ByteArrayOutputStream:

public class CopyStream extends ByteArrayOutputStream {
    public CopyStream(int size) { super(size); }

    /**
     * Get an input stream based on the contents of this output stream.
     * Do not use the output stream after calling this method.
     * @return an {@link InputStream}
     */
    public InputStream toInputStream() {
        return new ByteArrayInputStream(this.buf, 0, this.count);
    }
}

Write to the above output stream as needed, then call toInputStream to obtain an input stream over the underlying buffer. Consider the output stream as closed after that point.