public static List<File> files(String dirname) {
    if (dirname == null) {
        return Collections.emptyList();
    }

    File dir = new File(dirname);
    if (!dir.exists()) {
        return Collections.emptyList();
    }

    if (!dir.isDirectory()) {
        return Collections.singletonList(file(dirname));
    }

    return Arrays.stream(Objects.requireNonNull(dir.listFiles()))
        .collect(Collectors.toList());
}

这将读取指定路径下的指定文件扩展名文件(也可以查看子文件夹)

public static Map<String,List<File>> getFileNames(String 
dirName,Map<String,List<File>> filesContainer,final String fileExt){
    String dirPath = dirName;
    List<File>files = new ArrayList<>();
    Map<String,List<File>> completeFiles = filesContainer; 
    if(completeFiles == null) {
        completeFiles = new HashMap<>();
    }
    File file = new File(dirName);

    FileFilter fileFilter = new FileFilter() {
        @Override
        public boolean accept(File file) {
            boolean acceptFile = false;
            if(file.isDirectory()) {
                acceptFile = true;
            }else if (file.getName().toLowerCase().endsWith(fileExt))
              {
                acceptFile = true;
              }
            return acceptFile;
        }
    };
    for(File dirfile : file.listFiles(fileFilter)) {
        if(dirfile.isFile() && 
dirfile.getName().toLowerCase().endsWith(fileExt)) {
            files.add(dirfile);
        }else if(dirfile.isDirectory()) {
            if(!files.isEmpty()) {
                completeFiles.put(dirPath, files);  
            }

getFileNames(dirfile.getAbsolutePath(),completeFiles,fileExt);
        }
    }
    if(!files.isEmpty()) {
        completeFiles.put(dirPath, files);  
    }
    return completeFiles;
}

File folder = new File("/Users/you/folder/");
File[] listOfFiles = folder.listFiles();

for (File file : listOfFiles) {
    if (file.isFile()) {
        System.out.println(file.getName());
    }
}

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class AvoidNullExp {

public static void main(String[] args) {

    List<File> fileList =new ArrayList<>();
     final File folder = new File("g:/master");
     new AvoidNullExp().listFilesForFolder(folder, fileList);
}

    public void listFilesForFolder(final File folder,List<File> fileList) {
        File[] filesInFolder = folder.listFiles();
        if (filesInFolder != null) {
            for (final File fileEntry : filesInFolder) {
                if (fileEntry.isDirectory()) {
                    System.out.println("DIR : "+fileEntry.getName());
                listFilesForFolder(fileEntry,fileList);
            } else {
                System.out.println("FILE : "+fileEntry.getName());
                fileList.add(fileEntry);
            }
         }
        }
     }


}

一个注释根据获得目录中的所有文件。 方法files .walk(path)将通过遍历以给定起始文件为根的文件树来返回所有文件。

例如，下面有一个文件树:

\---folder
    |   file1.txt
    |   file2.txt
    |
    \---subfolder
            file3.txt
            file4.txt

使用java.nio.file.Files.walk(路径):

Files.walk(Paths.get("folder"))
        .filter(Files::isRegularFile)
        .forEach(System.out::println);

给出如下结果:

folder\file1.txt
folder\file2.txt
folder\subfolder\file3.txt
folder\subfolder\file4.txt

要获取当前目录下的所有文件，请使用java.nio.file.Files.list(Path):

Files.list(Paths.get("folder"))
        .filter(Files::isRegularFile)
        .forEach(System.out::println);

结果:

folder\file1.txt
folder\file2.txt

Java 8 Files.walk(..)很好，当你感到痛苦时，它不会抛出避免Java 8 Files.walk(..)终止原因(Java .nio.file. accessdeniedexception)。

这里有一个安全的解决方案，虽然没有Java 8Files.walk(..)那么优雅:

int[] count = {0};
try {
    Files.walkFileTree(Paths.get(dir.getPath()), new HashSet<FileVisitOption>(Arrays.asList(FileVisitOption.FOLLOW_LINKS)),
            Integer.MAX_VALUE, new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult visitFile(Path file , BasicFileAttributes attrs) throws IOException {
                    System.out.printf("Visiting file %s\n", file);
                    ++count[0];

                    return FileVisitResult.CONTINUE;
                }

                @Override
                public FileVisitResult visitFileFailed(Path file , IOException e) throws IOException {
                    System.err.printf("Visiting failed for %s\n", file);

                    return FileVisitResult.SKIP_SUBTREE;
                }

                @Override
                public FileVisitResult preVisitDirectory(Path dir , BasicFileAttributes attrs) throws IOException {
                     System.out.printf("About to visit directory %s\n", dir);
                    return FileVisitResult.CONTINUE;
                }
            });
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}