How do I read filenames from a folder and add them into an arraylist without having to make an array and looping all the answers into the arraylist?

Question

For example, lets say I have a list of txt files in a folder. What do I need to do in order for Java to read through each of the file names and add them into a string array list without having to do a String[] like other answers have suggested?

`Files.readAllLines()` is your friend (for reading a single file). — GhostCat, Jul 20 '18 at 19:24
@GhostCat I think OP wants to read the names of the files in a directory into an `ArrayList`, not the contents. — Jacob G., Jul 20 '18 at 19:25
Listing the files in a folder is a bit more work, but again, a solved and well documented problem. — GhostCat, Jul 20 '18 at 19:25
It's unclear. My best guess is to use `ArrayList` instead of `String[]` — zlakad, Jul 20 '18 at 19:25
@JacobG. Hmm, maybe. But still, getting file contents ... is also something that many other answers explain. — GhostCat, Jul 20 '18 at 19:26
No I don't want the file contents, I just want the names into an ArrayList, I couldn't find any threads on this. — Emir, Jul 20 '18 at 19:27
@GhostCat I agree, just wanted to update that duplicate, but it's good now. — Jacob G., Jul 20 '18 at 19:27
It seems to me that the linked answers do not provide the answer that the asker was looking for, namely a solution that does not involve writing a loop. I'd use: `Files.list(Paths.get("/path/to/folder")).filter(Files::isRegularFile).collect(Collectors.toList());` — akagixxer, Jul 20 '18 at 19:46
I agree with @akagixxer - the duplicates are all rather ancient and for modern Java, wrong. — Boris the Spider, Jul 20 '18 at 19:47
@akagixxer You should post that as an answer, since your code does the job the OP is looking for. — MC Emperor, Jul 21 '18 at 08:12
@MCEmperor sure thing. I think I couldn't earlier because the question was locked, marked as duplicate. — akagixxer, Jul 23 '18 at 14:37

score 0 · Answer 1 · edited Jul 22 '18 at 12:00

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File dir = new File(dir);
String[] fileArr  dir.listFiles();
List fileList = Arrays.toList(fileArr); //I bet this is instance of ArrayList

//ArrayList otherFileList = new ArrayList(fileList);
ArrayList otherFileList = new ArrayList();
otherFileList.addAll(fileList);

Note: those are the solutions where YOU don,t write the loop but the loop exists in the other methods.

edited Jul 22 '18 at 12:00

Andrew Thompson

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answered Jul 21 '18 at 06:54

monty

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score 0 · Answer 2 · answered Jul 23 '18 at 14:39

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If you are using Java 8 or newer you can use the java 'nio' library with java streams to get what you want.

E.g.

final List<Path> files = Files.list(Paths.get("/path/to/folder"))
  .filter(Files::isRegularFile)
  .collect(Collectors.toList());

answered Jul 23 '18 at 14:39

akagixxer

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How do I read filenames from a folder and add them into an arraylist without having to make an array and looping all the answers into the arraylist?

2 Answers2