Java.nio.files - Copying files

Question

Can anyone tell me what I've done wrong with the following code. I receive no errors - it just goes straight to the catch.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class Main {

    public static void main(String[] args) {
         Path source = Paths.get("C:\\Users\\Public\\Pictures\\SamplePictures");
    Path nwdir = Paths.get("D:\\NetbeansProjects\\CopyingFiles\\copiedImages");

    try{
    Files.copy(source, nwdir);
    }catch (IOException e){
        System.out.println("Unsucessful. What a surprise!");
    }
    }
}

Alfaro

If you print out e.getMessage() in the catch, then it might tell you. – Indeed

If you print your stacktrace, you might have a better clue as to what is going on. Add e.printStackTrace(System.out) into your catch block. – Dispersant

Have you tried, for example, e.printStackTrace() ? You'll get a better description of the problem. – Coherent

You receive no errors because you ignored them. ;) – Docila

Answer 1

If you take a look at the Javadocs of Files.copy, you'll notice this line (emphasis added):

If the file is a directory then it creates an empty directory in the target location (entries in the directory are not copied). This method can be used with the walkFileTree method to copy a directory and all entries in the directory, or an entire file-tree where required.

So it looks like you need to use that walkFileTree method.

(And as the commenters said, print out exceptions and they'll often tell you what's wrong!)

Zeal

java.nio.file.NoSuchFileException: C:\Users\Public\Pictures\SamplePictures at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:79) at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97) at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102) at sun.nio.fs.WindowsFileCopy.copy(WindowsFileCopy.java:99) at sun.nio.fs.WindowsFileSystemProvider.copy(WindowsFileSystemProvider.java:277) at java.nio.file.Files.copy(Files.java:1219) at Main.main(Main.java:14) – Alfaro

That's nice, but, as I said, your code will not work because you're trying to do a recursive copy with a function that cannot do recursive copies. Take a look at the API link that I provided. – Zeal

By recursive copy, do you mean the directory and the files and directories within samplepictures. If so - I have changed the path to link directly to a single .jpg file with the same error. Apologies if im missing your point. – Alfaro

No problem. What did you end up doing to fix it? – Zeal

The directory "Sample pictures" had a space in it. I thought java would complain because of the spaces, so I renamed it "SamplePictures". However, this didn't update the path. Another problem that occurred was my nwdir. I thought the path would be where I wanted the file. This is correct, but it also needs the file name. – Alfaro

Answer 2

Came across here looking for a NIO Java7 approach to recursively copy a directory to another location. This can be done with Files.walkFileTree as Jon7 mentioned in the other anwer. This code I got for a simple directory copy:

final Path srcDir, final Path dstDir;
Files.walkFileTree(srcDir, new SimpleFileVisitor<Path>() {
    public FileVisitResult visitFile( Path file, BasicFileAttributes attrs ) throws IOException {
        return copy(file);
    }
    public FileVisitResult preVisitDirectory( Path dir, BasicFileAttributes attrs ) throws IOException {
        return copy(dir);
    }
    private FileVisitResult copy( Path fileOrDir ) throws IOException {
        Files.copy( fileOrDir, dstDir.resolve( srcDir.relativize( fileOrDir ) ) );
        return FileVisitResult.CONTINUE;
    }
});

For a more detailed example which also handles file attributes and overwriting of existing files, see http://docs.oracle.com/javase/tutorial/essential/io/examples/Copy.java .

Procaine

Beware that srcDir.relativize( fileOrDir ) will throw a ProviderMismatchException if you use this to copy across different file systems, for example, from a ZipFile to default. – Maloy

Answer 3

This is how I have managed to copy a file from one location to another:

import java.io.IOException;
import static java.nio.file.StandardCopyOption.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class App  {

 public static void main(String[] args)
 {
    Path source = Paths.get("E:/myFile.pdf");
    Path nwdir = Paths.get("F:");
    try
    { 
       Files.copy(source, nwdir.resolve(source.getFileName()), REPLACE_EXISTING);
       System.out.println("File Copied");
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }
 }

}

Plethoric