Java - Read all .txt files in folder

I would take @Andrew White answer (+1 BTW) one step further, and suggest you would use FileNameFilter to list only relevant files:

FilenameFilter filter = new FilenameFilter() {
    public boolean accept(File dir, String name) {
        return name.endsWith(".txt");
    }
};

File folder = new File("/path/to/files");
File[] listOfFiles = folder.listFiles(filter);

for (int i = 0; i < listOfFiles.length; i++) {
    File file = listOfFiles[i];
    String content = FileUtils.readFileToString(file);
    // do something with the file
}

    final File folder = new File("C:/Dev Tools/apache-tomcat-6.0.37/webapps/ROOT/somefile");
    for (final File fileEntry : folder.listFiles()) {
           System.out.println("FileEntry Directory "+fileEntry);

With NIO you can do the following:

Files.walk(Paths.get("/path/to/files"))
          .filter(Files::isRegularFile)
          .filter(path -> path.getFileName().toString().endsWith(".txt"))
          .map(FileUtils::readFileToString)
          // do something

To read the file contents you may use Files#readString but, as usual, you need to handle IOException inside lambda expression.

Something like the following should get you going, note that I use apache commons FileUtils instead of messing with buffers and streams for simplicity...

File folder = new File("/path/to/files");
File[] listOfFiles = folder.listFiles();

for (int i = 0; i < listOfFiles.length; i++) {
  File file = listOfFiles[i];
  if (file.isFile() && file.getName().endsWith(".txt")) {
    String content = FileUtils.readFileToString(file);
    /* do somthing with content */
  } 
}