虽然有点晚了，但是这里比较了使用各种文件复制方法复制一个文件所花费的时间。我循环使用这些方法10次，然后取平均值。使用IO流的文件传输似乎是最糟糕的候选者:

方法如下:

private static long fileCopyUsingFileStreams(File fileToCopy, File newFile) throws IOException {
    FileInputStream input = new FileInputStream(fileToCopy);
    FileOutputStream output = new FileOutputStream(newFile);
    byte[] buf = new byte[1024];
    int bytesRead;
    long start = System.currentTimeMillis();
    while ((bytesRead = input.read(buf)) > 0)
    {
        output.write(buf, 0, bytesRead);
    }
    long end = System.currentTimeMillis();

    input.close();
    output.close();

    return (end-start);
}

private static long fileCopyUsingNIOChannelClass(File fileToCopy, File newFile) throws IOException
{
    FileInputStream inputStream = new FileInputStream(fileToCopy);
    FileChannel inChannel = inputStream.getChannel();

    FileOutputStream outputStream = new FileOutputStream(newFile);
    FileChannel outChannel = outputStream.getChannel();

    long start = System.currentTimeMillis();
    inChannel.transferTo(0, fileToCopy.length(), outChannel);
    long end = System.currentTimeMillis();

    inputStream.close();
    outputStream.close();

    return (end-start);
}

private static long fileCopyUsingApacheCommons(File fileToCopy, File newFile) throws IOException
{
    long start = System.currentTimeMillis();
    FileUtils.copyFile(fileToCopy, newFile);
    long end = System.currentTimeMillis();
    return (end-start);
}

private static long fileCopyUsingNIOFilesClass(File fileToCopy, File newFile) throws IOException
{
    Path source = Paths.get(fileToCopy.getPath());
    Path destination = Paths.get(newFile.getPath());
    long start = System.currentTimeMillis();
    Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
    long end = System.currentTimeMillis();

    return (end-start);
}

我在使用NIO通道类时看到的唯一缺点是，我似乎仍然无法找到一种方法来显示中间文件复制进度。

虽然有点晚了，但是这里比较了使用各种文件复制方法复制一个文件所花费的时间。我循环使用这些方法10次，然后取平均值。使用IO流的文件传输似乎是最糟糕的候选者:

方法如下:

private static long fileCopyUsingFileStreams(File fileToCopy, File newFile) throws IOException {
    FileInputStream input = new FileInputStream(fileToCopy);
    FileOutputStream output = new FileOutputStream(newFile);
    byte[] buf = new byte[1024];
    int bytesRead;
    long start = System.currentTimeMillis();
    while ((bytesRead = input.read(buf)) > 0)
    {
        output.write(buf, 0, bytesRead);
    }
    long end = System.currentTimeMillis();

    input.close();
    output.close();

    return (end-start);
}

private static long fileCopyUsingNIOChannelClass(File fileToCopy, File newFile) throws IOException
{
    FileInputStream inputStream = new FileInputStream(fileToCopy);
    FileChannel inChannel = inputStream.getChannel();

    FileOutputStream outputStream = new FileOutputStream(newFile);
    FileChannel outChannel = outputStream.getChannel();

    long start = System.currentTimeMillis();
    inChannel.transferTo(0, fileToCopy.length(), outChannel);
    long end = System.currentTimeMillis();

    inputStream.close();
    outputStream.close();

    return (end-start);
}

private static long fileCopyUsingApacheCommons(File fileToCopy, File newFile) throws IOException
{
    long start = System.currentTimeMillis();
    FileUtils.copyFile(fileToCopy, newFile);
    long end = System.currentTimeMillis();
    return (end-start);
}

private static long fileCopyUsingNIOFilesClass(File fileToCopy, File newFile) throws IOException
{
    Path source = Paths.get(fileToCopy.getPath());
    Path destination = Paths.get(newFile.getPath());
    long start = System.currentTimeMillis();
    Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
    long end = System.currentTimeMillis();

    return (end-start);
}

我在使用NIO通道类时看到的唯一缺点是，我似乎仍然无法找到一种方法来显示中间文件复制进度。

如果你在一个已经使用Spring的web应用程序中，如果你不想包含Apache Commons IO来进行简单的文件复制，你可以使用Spring框架的FileCopyUtils。

在Java 7中作为标准提供，path.copyTo: http://openjdk.java.net/projects/nio/javadoc/java/nio/file/Path.html http://java.sun.com/docs/books/tutorial/essential/io/copy.html

我不敢相信他们花了这么长时间来标准化像文件复制这样常见而简单的事情:(

要复制文件并将其保存到目标路径，您可以使用下面的方法。

public void copy(File src, File dst) throws IOException {
    InputStream in = new FileInputStream(src);
    try {
        OutputStream out = new FileOutputStream(dst);
        try {
            // Transfer bytes from in to out
            byte[] buf = new byte[1024];
            int len;
            while ((len = in.read(buf)) > 0) {
                out.write(buf, 0, len);
            }
        } finally {
            out.close();
        }
    } finally {
        in.close();
    }
}

根据我的测试，带缓冲区的NIO复制是最快的。下面的工作代码来自我在https://github.com/mhisoft/fastcopy上的一个测试项目

import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.text.DecimalFormat;


public class test {

private static final int BUFFER = 4096*16;
static final DecimalFormat df = new DecimalFormat("#,###.##");
public static void nioBufferCopy(final File source, final File target )  {
    FileChannel in = null;
    FileChannel out = null;
    double  size=0;
    long overallT1 =  System.currentTimeMillis();

    try {
        in = new FileInputStream(source).getChannel();
        out = new FileOutputStream(target).getChannel();
        size = in.size();
        double size2InKB = size / 1024 ;
        ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER);

        while (in.read(buffer) != -1) {
            buffer.flip();

            while(buffer.hasRemaining()){
                out.write(buffer);
            }

            buffer.clear();
        }
        long overallT2 =  System.currentTimeMillis();
        System.out.println(String.format("Copied %s KB in %s millisecs", df.format(size2InKB),  (overallT2 - overallT1)));
    }
    catch (IOException e) {
        e.printStackTrace();
    }

    finally {
        close(in);
        close(out);
    }
}

private static void close(Closeable closable)  {
    if (closable != null) {
        try {
            closable.close();
        } catch (IOException e) {
            if (FastCopy.debug)
                e.printStackTrace();
        }    
    }
}

}