DirectoryStreamFilter

DirectoryStreamFilter is an interface in Java's NIO.2 API, introduced in Java 7, that allows for filtering entries within a directory. It is primarily used in conjunction with the Files.newDirectoryStream() method. This interface defines a single method, accept(), which takes a Path object as an argument. The accept() method returns true if the Path object should be included in the stream, and false otherwise.

When iterating over a directory's contents using Files.newDirectoryStream(), you can provide an instance of a class that implements DirectoryStreamFilter. The stream will then only yield Path objects for which the filter's accept() method returns true. This is a powerful mechanism for selectively processing files or subdirectories based on various criteria, such as file name patterns, file types, or modification dates.

Common use cases for DirectoryStreamFilter include finding all files with a specific extension, excluding hidden files, or processing only directories. Implementing this interface allows developers to create custom filtering logic, making directory traversal more efficient and targeted by avoiding the need to manually filter the entire stream of entries after retrieval. The filter is applied during the stream creation process.