import java.io.File;
import java.io.FilenameFilter;

public class ListFiles{
    public static void main(String args[]){
        File directory = new File(args[0]);
        for(File file : directory.listFiles(getRegexFilter(".*\\.xls"))){
            System.out.println(file.getAbsolutePath());
        }
    }

    private static FilenameFilter getRegexFilter(String regex) {
        final String regex_ = regex;
        return new FilenameFilter() {
            public boolean accept(File dir, String name) {
                return name.matches(regex_);
            }
        };
    }
}