Here's an example of how to use the PrefixFileFilter class from the Apache Commons IO library to filter files based on their name prefix:

import java.io.File;
import org.apache.commons.io.filefilter.PrefixFileFilter;

public class Main {
    public static void main(String[] args) {
        // The name prefix to search for
        String prefix = "file";

        File dir = new File("/path/to/directory");
        File[] matchingFiles = dir.listFiles((FileFilter) new PrefixFileFilter(prefix));

        for (File file : matchingFiles) {
            System.out.println(file.getName());
        }
    }
}

In this example, /path/to/directory should be replaced with the path to the directory you want to search through. The listFiles method is called on the dir object, and it takes an instance of PrefixFileFilter as an argument. The PrefixFileFilter constructor takes a string as an argument, which is the prefix to search for. The filtered matching files are stored in the matchingFiles array, and their names are printed out using a for loop.

You can use the PrefixFileFilter to filter files based on the prefix of their names, this can be useful when you want to select files that have certain characteristic in the beginning of their name, for example to select all files that start with "backup_".

File[] matchingFiles = dir.listFiles((FileFilter) new PrefixFileFilter("backup_"));

This will return all files that start with "backup_".