How to copy Sheets form one Workbook to an other - Or: Copying OPCPackage PackageParts consumes a lot of memory. Why?

[Jan Kunzmann]

Hi,

this is my firtst mail to a mailing list.

I asumed that just copy via streaming would consume only little memory. Why
do i get 750m ram consumption for a 12m file?
Is there any way to replace a Sheet in a Workbook without consuming tons of
memory?

        try (OPCPackage pkg = OPCPackage.open (sourceFilename,
PackageAccess.READ)) {
            PackagePart srcPart = getPackagePart(pkg, sheetName);
            try (OPCPackage dest = OPCPackage.open(destFilename)) {
                PackagePart destPart = getPackagePart(dest, sheetName);
                try (OutputStream os = destPart.getOutputStream();
InputStream is = srcPart.getInputStream()) {
                    byte buf[] = new byte[1024];
                    for (int readBytes; (readBytes = is.read(buf)) != -1;
                            os.write(buf, 0, readBytes))
                            os.flush();
                        ;
                }
            }
        }

regards,
Jan