Java Copy File – 4 Ways to Copy File in Java

Filed Under: Java

Java copy file is a very common operation. But java.io.File class doesn’t have any shortcut method to copy a file from source to destination. Here we will learn about four different ways we can copy file in java.

Java Copy File

java copy file, copy file in java, java file copy, java copy file to directory

  1. Java Copy File – Stream

This is the conventional way of file copy in java. Here we create two Files – source and destination. Then we create InputStream from source and write it to the destination file using OutputStream for java copy file operation.

Here is the method that can be used for java copy file using streams.


private static void copyFileUsingStream(File source, File dest) throws IOException {
    InputStream is = null;
    OutputStream os = null;
    try {
        is = new FileInputStream(source);
        os = new FileOutputStream(dest);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = is.read(buffer)) > 0) {
            os.write(buffer, 0, length);
        }
    } finally {
        is.close();
        os.close();
    }
}
  1. Java Copy File – java.nio.channels.FileChannel

Java NIO classes were introduced in Java 1.4 and FileChannel can be used to copy file in java. According to transferFrom() method javadoc, this way of copy file is supposed to be faster than using Streams for java copy files.

Here is the method that can be used to copy a file using FileChannel.


private static void copyFileUsingChannel(File source, File dest) throws IOException {
    FileChannel sourceChannel = null;
    FileChannel destChannel = null;
    try {
        sourceChannel = new FileInputStream(source).getChannel();
        destChannel = new FileOutputStream(dest).getChannel();
        destChannel.transferFrom(sourceChannel, 0, sourceChannel.size());
       }finally{
           sourceChannel.close();
           destChannel.close();
   }
}
  1. Java Copy File – Apache Commons IO FileUtils

Apache Commons IO FileUtils.copyFile(File srcFile, File destFile) can be used to copy file in java. If you are already using Apache Commons IO in your project, it makes sense to use this for code simplicity. Internally it uses Java NIO FileChannel, so you can avoid this wrapper method if you are not already using it for other functions.

Here is the method for using apache commons io for java copy file operation.


private static void copyFileUsingApacheCommonsIO(File source, File dest) throws IOException {
    FileUtils.copyFile(source, dest);
}
  1. Java Copy File – Files class

If you are working on Java 7 or higher, you can use Files class copy() method to copy file in java. It uses File System providers to copy the files.


private static void copyFileUsingJava7Files(File source, File dest) throws IOException {
    Files.copy(source.toPath(), dest.toPath());
}

Now to find out which is the fastest method, I wrote a test class and executed above methods one-by-one for copy file of 1 GB. In each call, I used different files to avoid any benefit to later methods because of caching.


package com.journaldev.files;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.FileChannel;
import java.nio.file.Files;

import org.apache.commons.io.FileUtils;

public class JavaCopyFile {

    public static void main(String[] args) throws InterruptedException, IOException {
        File source = new File("/Users/pankaj/tmp/source.avi");
        File dest = new File("/Users/pankaj/tmp/dest.avi");

        //copy file conventional way using Stream
        long start = System.nanoTime();
        copyFileUsingStream(source, dest);
        System.out.println("Time taken by Stream Copy = "+(System.nanoTime()-start));
        
        //copy files using java.nio FileChannel
        source = new File("/Users/pankaj/tmp/sourceChannel.avi");
        dest = new File("/Users/pankaj/tmp/destChannel.avi");
        start = System.nanoTime();
        copyFileUsingChannel(source, dest);
        System.out.println("Time taken by Channel Copy = "+(System.nanoTime()-start));
        
        //copy files using apache commons io
        source = new File("/Users/pankaj/tmp/sourceApache.avi");
        dest = new File("/Users/pankaj/tmp/destApache.avi");
        start = System.nanoTime();
        copyFileUsingApacheCommonsIO(source, dest);
        System.out.println("Time taken by Apache Commons IO Copy = "+(System.nanoTime()-start));
        
        //using Java 7 Files class
        source = new File("/Users/pankaj/tmp/sourceJava7.avi");
        dest = new File("/Users/pankaj/tmp/destJava7.avi");
        start = System.nanoTime();
        copyFileUsingJava7Files(source, dest);
        System.out.println("Time taken by Java7 Files Copy = "+(System.nanoTime()-start));        
    }
}

Here is the output of the above program, note that I commented above code to make sure every time only one method is used for java file copy operation.


Time taken by Stream Copy = 44582575000
Time taken by Channel Copy = 104138195000
Time taken by Apache Commons IO Copy = 108396714000
Time taken by Java7 Files Copy = 89061578000

From the output, it’s clear that Stream Copy is the best way to copy File in Java. But it’s a very basic test. If you are working on a performance intensive project, then you should try out different methods for java copy file and note down the timings to figure out the best approach for your project.

You should also play around different ways of java copy files based on your average size of the file.

I have created a YouTube video for 4 ways to copy the file in java, you can watch it to learn more.

Comments

  1. Olaf Leimann says:

    It has been touched on before in the comment above, but when you determine the read/write buffer size, I found that you better stick with at least 64K (65536) due to that being the largest NTFS cluster size (4kb default, also in most other file systems).

    In fact, it’s even faster with normal I/O streams if you go by Megabyte – you can reach 150 Mb/s on fast disks/RAID arrays in spindles, and more on SSD.

    The Java 7 copyFile method looks nice, but you loose control over e.g. influencing the bandwidth, if you want to throttle copying, which you can do by calculating the milliseconds you want for 1Mb, for example, and wait out the rest of those milliseconds if you’re faster. This will allow for not slowing down a work system.
    Also, instead of copying when inside the same file system (disk/raid array/NFS mount/CIFS mount) in Java 7 you can hardlink instead, saving space (useful for separate play lists of media).

  2. Ana says:

    import java.util.*;
    import java.io.*;
    class FILE4
    {
    public static void main(String args[])throws Exception
    {
    Scanner s1=new Scanner(System.in);
    FileOutputStream f1=new FileOutputStream(“E:/A2.txt”,true);
    DataOutputStream d1=new DataOutputStream(f1);
    char choice;
    int rno;
    String name;
    do
    {
    System.out.println(“Enter a roll number and name:”);
    rno=s1.nextInt();
    name=s1.nextLine();
    d1.writeInt(rno);
    d1.writeUTF(name);
    System.out.println(“Continue???”);
    choice=s1.next().charAt(0);
    }while(choice==’y’||choice==’Y’);
    System.out.println(“DO YOU WANT TO READ THIS BINARY FILE??\nIF YES THEN TYPE ‘YES’ OTHERWISE TYPE ‘NO’—>”);
    String ch=s1.next();
    if(ch.equalsIgnoreCase(“yes”))
    {
    try
    {
    FileInputStream F1=new FileInputStream(“E:/A2.txt”);
    DataInputStream D1=new DataInputStream(F1);
    boolean eof=true;
    while(eof)
    {
    try
    {
    int rn=D1.readInt();
    String nm=D1.readUTF();
    System.out.println(“ROLL NO. “+rn+”\nNAME “+nm);
    }
    catch(EOFException x)
    {
    eof=false;
    }
    }
    }
    catch(FileNotFoundException e)
    {
    System.out.println(“File Does Not Found”);
    }
    }
    if(ch.equalsIgnoreCase(“No”))
    {
    System.out.println(“Byeee!!!!!”);
    System.exit(0);
    }
    FileOutputStream F=new FileOutputStream(“E:/A3.txt”,true);
    DataOutputStream D=new DataOutputStream(F);
    boolean e=true;
    try
    {
    FileInputStream F1=new FileInputStream(“E:/A2.txt”);
    DataInputStream D1=new DataInputStream(F1);
    while(e)
    {
    int rns=D1.readInt();
    String nms=D1.readUTF();
    D.writeInt(rns);
    D.writeUTF(nms);
    }
    }
    catch(EOFException x)
    {
    e=false;
    }
    System.out.println(“DO YOU WANT TO READ THE COPIED BINARY FILE??\nIF YES THEN TYPE ‘YES’ OTHERWISE TYPE ‘NO’—>”);
    String ch1=s1.next();
    if(ch.equalsIgnoreCase(“yes”))
    {
    try
    {
    FileInputStream F12=new FileInputStream(“E:/A3.txt”);
    DataInputStream D12=new DataInputStream(F12);
    boolean eof=true;
    while(eof)
    {
    try
    {
    int rnI=D12.readInt();
    String nmI=D12.readUTF();
    System.out.println(“ROLL NO. “+rnI+”\nNAME “+nmI);
    }
    catch(EOFException x)
    {
    eof=false;
    }
    }
    }
    catch(FileNotFoundException x)
    {
    System.out.println(“File Does Not Found”);
    }
    }
    if(ch.equalsIgnoreCase(“No”))
    {
    System.out.println(“Byeee!!!!!”);
    System.exit(0);
    }
    }
    }

  3. Harri says:

    Hi! Replace > with >= in copyFileUsingStream;

    while ((length = is.read(buffer)) >= 0)

    1. Alessandro says:

      Good catch!

  4. Zarquon says:

    There is an error in your FileChannel example, since one call to transferFrom is not guaranteed to be sufficient – it should be in a loop.

  5. Haibo Yan says:

    I am sorry I have to say this is misleading. 1. First benchmark on files highly depends on filesystem and disk type you’re using. Assume you are using buffer for all code, streaming may be faster. But if your filesystem supports DMA, Java may use DMA in FileChannel.transferTo/transferFrom, this maybe much faster than using streaming.

  6. Eyosiyas says:

    How to write a multithreaded java program which opens a USB drive (flash drive) automatically after it is plugged into the machine, scans all files in the disk, and copy content each file to corresponding files in the local disk simultaneously. Thanks for your help.

  7. Ngọc Khương says:

    Thank you very much.

  8. Rajeshkannan Balu says:

    Working gud, I used stream method ,Thanks,,,,,….

  9. user02 says:

    Hi Pankaj,

    Did you take into account file and free space fragmentation and position of files on disk during your tests? I think it would be better to copy one file and reboot the computer between tests. Or perform tests on SSD.

  10. Yung says:

    Making a change on Stream method “byte[] buffer = new byte[16384];” and then run the test

    Time taken by Stream Copy = 217746669
    Time taken by Channel Copy = 207893741
    Time taken by Java7 Files Copy =201835429

    the stream method need more investigation to speed up.

  11. thomaschen says:

    Environment:
    Run timestamp: 2014-11-24 23:40:09.038
    JVM: 1.7.0_67-b01
    OS: amd64

    Test Result(unit:seconds)
    jdk7_files : 53.55 [+- 10.00]
    stream : 60.49 [+- 13.03]
    channel : 60.56 [+- 6.83]
    commons_io : 62.92 [+- 10.75]

  12. tnik says:

    I guess it depends from the hardware (if channel copy is supported) and from the Java version:

    I changed the time to millis

    I got for

    Java 1.6_45
    Time taken by Channel Copy = 3314
    Time taken by Stream Copy = 4734
    Time taken by Apache Commons IO Copy = 3769

    Java 1.7.0
    Time taken by Channel Copy = 318
    Time taken by Stream Copy = 4310
    Time taken by Apache Commons IO Copy = 326
    Time taken by Java7 Files Copy = 2088

    Java 1.8.0_20
    Time taken by Channel Copy = 335
    Time taken by Stream Copy = 4714
    Time taken by Apache Commons IO Copy = 342
    Time taken by Java7 Files Copy = 2395

  13. Venki says:

    Hi All,
    How to copy directories and file from one location to another location on same ftp server?

  14. Ram Mahesh Kumar says:

    Could you please explain me the situations at which an IOException can happen during a file copy.

    1. Aliasger Motiwala says:

      attempting to read from a file that does not exist
      attempting to write to a file that has an invalid name (a slash or a question mark in the title should do it)
      attempting to read the next token in a file when there are no more tokens.

      Happy learning 🙂

  15. Vijayakumar says:

    Great post . I will try and get the faster one.

  16. Michael says:

    Hi Pankaj, thanks a lot for those helpful examples.

  17. đông says:

    Hi Pankaj…can you explain : how to copy a large file (~3GB .avi) to another loacation?? Example : from C: to D:
    Thanks

  18. Curious says:

    Hey Pankaj,

    no one has rerun your tests, but we’re all curious since the numbers you published are the exact opposite of what you say in the text. Did you mess up reading your numbers, or did you make a mistake in writing them down?

    According to your figures stream copy is over twice as fast as everything else?

    1. Pankaj says:

      mistake in posting, updated.

  19. Mike Nixon says:

    Thanks for an interesting look at the different methods.
    I ran your program on my laptop, and stream copy was by far the fastest

    Time taken by Stream Copy = 3,337,266,041 (3 billion…….)
    Time taken by Channel Copy = 18,994,299,884 (18 billion…..)
    Time taken by Java7 Files Copy = 15,816,023,905 (15 billion…..)

    Looking at the above figures, Stream copy is 6x faster than Channel copy, and 5x faster than Java7 Files copy. Several runs came up with similar figures.

    1. Pankaj says:

      I missed the additional digit, updated the post.

  20. Brian says:

    None of these people ran your program. You’re missing the point.

    These are the numbers, copied and pasted, that you posted in your article above:


    Time taken by Stream Copy = 44582575000
    Time taken by Channel Copy = 104138195000
    Time taken by Apache Commons IO Copy = 108396714000
    Time taken by Java7 Files Copy = 89061578000

    If you list the numbers first, you get this (zeroes inserted at the beginning to align the numbers):


    044582575000 = Time taken by Stream Copy
    104138195000 = Time taken by Channel Copy
    108396714000 = Time taken by Apache Commons IO Copy
    089061578000 = Time taken by Java7 Files Copy

    This shows that your Stream Copy test took much less time than the two Channel Copy tests. How did you conclude that Channel Copy is the fastest? Your very own run of the test contradicts that.

  21. Me says:

    Time taken by Stream Copy …………… 44,582,575,000
    Time taken by Channel Copy …………. 104,138,195,000
    Time taken by Apache Commons IO Copy … 108,396,714,000
    Time taken by Java7 Files Copy ………. 89,061,578,000

  22. Joel Shprentz says:

    When I align the time values, it appears that the stream copy is the fasted, not the channel copy.


    Time taken by Stream Copy = 44582575000
    Time taken by Channel Copy = 104138195000
    Time taken by Apache Commons IO Copy = 108396714000
    Time taken by Java7 Files Copy = 8906157800

    1. Pankaj says:

      Did you run the same program? Did you commented other ways to copy and ran each method one by one?

      1. Joel Shprentz says:

        I did not rerun your tests. I copied your results above and reformatted the display to reveal that Stream Copy has the lowest time:


        Time taken by Stream Copy ............... 44582575000
        Time taken by Channel Copy ............. 104138195000
        Time taken by Apache Commons IO Copy ... 108396714000
        Time taken by Java7 Files Copy .......... 89061578000

        1. Adtc says:

          I too took your results and aligned the numbers. Stream Copy took only half the time of Java7 file copy. Channel copy seems to be slowest! Can you verify your results that you didn’t mess up something or interpret wrongly?


          Time taken by Stream Copy 44,582,575,000
          Time taken by Channel Copy 104,138,195,000
          Time taken by Apache Commons IO Copy 108,396,714,000
          Time taken by Java7 Files Copy 89,061,578,000

          1. Pankaj says:

            Did you run them separately each one by one?

          2. Pankaj says:

            Yeah I got it now, I missed the extra bit in all other copy methods, updated the post.
            Thanks a lot.

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