Java: return a LinkedHashSet - list

Question

Basically, I'm trying to return a collection of strings in Java.
But...
each string must be unique because they're all the names of ".db" files in current folder, so I thought this collection should be LinkedHashSet.
The elements (filenames) must maintain the exact same order, so I can choose one of them by it's order number in the collection.
My main routine will show this collection in a GUI component (maybe a JList) for the user to choose one of them (without the .db extension).
I'm totally newbie (as you can see), so if you think there are better options than LinkedHashSet please tell me.
Also, how can I grab this collection in the main class?
What I've got so far:
public Set GetDBFilesList() {
//returns ORDERED collection of UNIQUE strings with db filenames
LinkedHashSet a = new LinkedHashSet();
FilenameFilter dbFilter = (File file, String name) -> {
return name.toLowerCase().endsWith(".db");
};
String dirPath = "";
File dir = new File(dirPath);
File[] files = dir.listFiles(dbFilter);
if (files.length > 0) {
for (File aFile : files) {
a.add(aFile.getName());
}
}
return a;
}

Answer 1

You want an ordered and unique collection - LinkedHashSet is a good choice.
Some comments on your methode:
Your should use Generics f.e.: LinkedHashSet<File> or LinkedHashSet<String>
The check for files.length is unnecessary, but you could check for null if the path is not a directory or an I/O error occured
You should name your variables properly: a is not a good name
Your methode can be static - maybe in a static helper class?
The Set.add methode returns true or false if the item was added or not, you should check that just in case
Putting all together:
//Your Main class
public class Main
{
public static void main(String[] args)
{
File dir = new File("");
Collection<File> dbFiles = DbFileManager.getDatabaseFiles(dir);
}
}
//Your DB File Reader Logic
public class DbFileManager
{
public static Collection<File> getDatabaseFiles(File directory)
{
Collection<File> dbFiles = new LinkedHashSet<>();
//filter code etc.
boolean success = dbFiles.addAll(directory.listFiles(filter));
//Check if everthing was added
return dbFiles;
}
}