将字节数组输入流拷贝成字节数组输出流，将ByteArrayInputStream转成ByteArrayOutputStream

    /** 将 ByteArrayInputStream 拷贝成 ByteArrayOutputStream
     *  将 字节数组输入流 拷贝成 字节数组输出流
     */
    public static ByteArrayOutputStream getByteArrayOutputStream(ByteArrayInputStream inputStream) throws IOException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, length);
        }
        return outputStream;
    }