Java复制文件或目录

利用java复制文件或目录，要么使用递归的方法，要么使用walkFileTree的方法。大家可以比较一下。

package gy.finolo;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;

import static java.nio.file.FileVisitResult.CONTINUE;

public class CopyUtils {

    public static void copy2Directory(Path inPath, Path outDirPath) throws IOException {

        // 确保输出目录存在, 如果inPath是File的话, 这里就执行一次, 所以不用写到copyFile2Diretory()方法里
        if (!Files.exists(outDirPath)) {
            Files.createDirectories(outDirPath);
        }

        if (Files.isDirectory(inPath)) {
            copyFilesInDirectory2Directory(inPath, outDirPath);
        } else {
            copyFile2Directory(inPath, outDirPath);
        }


    }

    private static void copyFilesInDirectory2Directory(Path inDirPath, Path outDirPath) throws IOException {
        DirectoryStream<Path> paths = Files.newDirectoryStream(inDirPath);
        for (Path path : paths) {

            if (Files.isDirectory(path)) {
                Path subOutDirPath = outDirPath.resolve(inDirPath.relativize(path));
                // 确保输出目录存在
                if (!Files.exists(subOutDirPath)) {
                    Files.createDirectories(subOutDirPath);
                }
                copyFilesInDirectory2Directory(path, subOutDirPath);
            } else {
                Path subOutDirPath = outDirPath.resolve(inDirPath.relativize(path.getParent()));
                copyFile2Directory(path, subOutDirPath);
            }
        }
    }

    private static void copyFile2Directory(Path inFilePath, Path outDirPath) throws IOException {
        Path fileName = inFilePath.getFileName();
        Path outFilePath = outDirPath.resolve(fileName);

        int bufSize = 8 * 1024;
        byte[] buffer = new byte[bufSize];
        int len;

        try (InputStream is = Files.newInputStream(inFilePath);
             OutputStream os = Files.newOutputStream(outFilePath, StandardOpenOption.TRUNCATE_EXISTING,
                     StandardOpenOption.WRITE,
                     StandardOpenOption.CREATE)) {
            while ((len = is.read(buffer)) > 0) {
                os.write(buffer, 0, len);
            }
        }
    }
    
    /**
     * 注意: visitFile方法中, 每次需要做一个if (inPath.equals(file))的判断, 
     * 如果inPath是文件, 那返回为true, 如果inPath为目录, 那永远返回false
     * 我是为了统计, 才在里面加了一个判断, 在实际运用中, 有了这个判断效率就不高了。
     * @param inPath
     * @param outDirPath
     * @throws IOException
     */
    public static void copy2DirectoryV2(Path inPath, Path outDirPath) throws IOException {
        // 确保输出目录存在
        if (!Files.exists(outDirPath)) {
            Files.createDirectories(outDirPath);
        }

        Files.walkFileTree(inPath, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                    throws IOException {
                System.out.println("processing DIR: " + dir);
                Path subOutDirPath = outDirPath.resolve(inPath.relativize(dir));

                if (!Files.exists(subOutDirPath)) {
                    Files.createDirectories(subOutDirPath);
                }
                return CONTINUE;
            }

            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                    throws IOException {
                System.out.println("processing FILE: " + file);
                Path outPath;
                if (inPath.equals(file)) {
                    // 说明source是一个文件, 只需要单独复制一个文件即可
                    outPath = outDirPath.resolve(file.getFileName());
                } else {
                    outPath = outDirPath.resolve(inPath.relativize(file));
                }
                Files.copy(file, outPath);
                return CONTINUE;
            }
        });
    }

    public static void main(String[] args) {

        Path inPath = Paths.get("/usr/local");
        Path outDirPath = Paths.get("/opt");

        try {
            // CopyUtils.copy2Directory(inPath, outDirPath);
            CopyUtils.copy2DirectoryV2(inPath, outDirPath);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}