虽然我同意Rich, Orian和其他人使用:

    final File keysFileFolder = new File(<path>); 
    File[] fileslist = keysFileFolder.listFiles();

    if(fileslist != null)
    {
        //Do your thing here...
    }

出于某种原因，这里所有的例子都使用绝对路径(即从根目录开始，或者，对于windows..)

我想补充的是，也可以使用相对路径。 所以，如果你的pwd(当前目录/文件夹)是folder1，你想要解析folder1/子文件夹，你只需写(在上面的代码中代替):

    final File keysFileFolder = new File("subfolder");

void getFiles(){
        String dirPath = "E:/folder_name";
        File dir = new File(dirPath);
        String[] files = dir.list();
        if (files.length == 0) {
            System.out.println("The directory is empty");
        } else {
            for (String aFile : files) {
                System.out.println(aFile);
            }
        }
    }

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

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

public void listFilesForFolder(final File folder) {
    for (final File fileEntry : folder.listFiles()) {
        if (fileEntry.isDirectory()) {
            listFilesForFolder(fileEntry);
        } else {
            System.out.println(fileEntry.getName());
        }
    }
}

final File folder = new File("/home/you/Desktop");
listFilesForFolder(folder);

文件。walk API可从Java 8获得。

try (Stream<Path> paths = Files.walk(Paths.get("/home/you/Desktop"))) {
    paths
        .filter(Files::isRegularFile)
        .forEach(System.out::println);
} 

这个例子使用了API指南中推荐的try-with-resources模式。它确保在任何情况下流都将被关闭。

File directory = new File("/user/folder");      
File[] myarray;  
myarray=new File[10];
myarray=directory.listFiles();
for (int j = 0; j < myarray.length; j++)
{
       File path=myarray[j];
       FileReader fr = new FileReader(path);
       BufferedReader br = new BufferedReader(fr);
       String s = "";
       while (br.ready()) {
          s += br.readLine() + "\n";
       }
}

import java.io.File;


public class ReadFilesFromFolder {
  public static File folder = new File("C:/Documents and Settings/My Documents/Downloads");
  static String temp = "";

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    System.out.println("Reading files under the folder "+ folder.getAbsolutePath());
    listFilesForFolder(folder);
  }

  public static void listFilesForFolder(final File folder) {

    for (final File fileEntry : folder.listFiles()) {
      if (fileEntry.isDirectory()) {
        // System.out.println("Reading files under the folder "+folder.getAbsolutePath());
        listFilesForFolder(fileEntry);
      } else {
        if (fileEntry.isFile()) {
          temp = fileEntry.getName();
          if ((temp.substring(temp.lastIndexOf('.') + 1, temp.length()).toLowerCase()).equals("txt"))
            System.out.println("File= " + folder.getAbsolutePath()+ "\\" + fileEntry.getName());
        }

      }
    }
  }
}