Java copy part of InputStream to OutputStream

Question

I have a file with 3236000 bytes and I want to read 2936000 from start and write to an OutputStream

InputStream is = new FileInputStream(file1);
OutputStream os = new FileOutputStream(file2);

AFunctionToCopy(is,os,0,2936000); /* a function or sourcecode to write input stream 0to2936000 bytes */

I can read and write byte by byte, but it's to slow (i think) from buffered reading How can do I copy it?

I want to copy part of an InputStream to OutputStream

Curious
– Curious

2014-03-25 21:05:49 +00:00
Commented Mar 25, 2014 at 21:05 — Curious
– Curious, Commented Mar 25, 2014 at 21:05

nimsson · Accepted Answer · 2014-03-25 21:15:39Z

2

public static void copyStream(InputStream input, OutputStream output, long start, long end)
    throws IOException
{
    for(int i = 0; i<start;i++) input.read(); // dispose of the unwanted bytes
    byte[] buffer = new byte[1024]; // Adjust if you want
    int bytesRead;
    while ((bytesRead = input.read(buffer)) != -1 && bytesRead<=end) // test for EOF or end reached
    {
        output.write(buffer, 0, bytesRead);
    }
}

should work for you.

answered Mar 25, 2014 at 21:15

nimsson

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3 Comments

Curious Over a year ago

bytesRead<=end just check while step readed bytes be <= than end not all readed bytes.

nimsson Over a year ago

yes @Curious it will dispose of the first bytes and then uses a buffer of 1024 bytes to write the outputstream You might also check out the Channel class.

MasterHD Over a year ago

Your start argument is actually the number of bytes to skip before copying and it would be more efficient to do that with input.skip(start);

MasterHD · Accepted Answer · 2021-09-07 14:28:51Z

1

If you have access to the Apache Commons library, you can use:

IOUtils.copyLarge(InputStream input, OutputStream output, long inputOffset, long length)

answered Sep 7, 2021 at 14:28

MasterHD

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