Apache Commons IO-PrefixFileFilter

The PrefixFileFilter is a class provided by the Apache Commons IO library, which allows developers to filter files based on their filename prefix.

Usage

To use the PrefixFileFilter, you need to first add the commons-io dependency to your project. Once you have done that, you can create a new instance of the filter and pass it to a FileUtils method that accepts a FileFilter.

Here is an example code snippet that demonstrates how to use the PrefixFileFilter class:

import org.apache.commons.io.filefilter.PrefixFileFilter;
import org.apache.commons.io.FileUtils;

import java.io.File;

public class FileFilterExample {
    public static void main(String[] args) {
        String prefix = "my_file_prefix";
        File dir = new File("/path/to/directory");

        // Create a new PrefixFileFilter instance
        PrefixFileFilter filter = new PrefixFileFilter(prefix);

        // Use the filter to get a list of files that match the prefix
        File[] files = FileUtils.listFiles(dir, filter, null);

        // Do something with the filtered files...
    }
}

Constructor

The PrefixFileFilter class provides several constructor overloads that allow you to create a filter instance with a specific prefix string. Here are the available constructors:

PrefixFileFilter(String prefix)
PrefixFileFilter(String[] prefixes)
PrefixFileFilter(List<String> prefixes)

Other methods

Besides the constructor, the PrefixFileFilter class also provides the following methods:

public boolean accept(File file)

This method is called by the FileUtils methods that accept a FileFilter. The method returns true if the specified file's name starts with the prefix string that was passed to the filter's constructor.

public boolean accept(File dir, String name)

This is an overloaded accept() method that accepts the parent directory and the filename as separate parameters. The method returns true if the specified filename starts with the prefix string that was passed to the filter's constructor.

Conclusion

The PrefixFileFilter class provided by the Apache Commons IO library allows you to filter files based on their filename prefix. This can be useful when you need to work with a subset of files in a directory that share a common prefix.