I am reading a newline-separated text file into a String-array.
Since I know the delimiter will always be \n, I should be able to append each word to a StringBuilder, then split it using the delimiter.
Simply put, which method should I use and why?
Method A:
1. Create an ArrayList (or another more suited Collection)
2. Append each row to the list
3. Return list.toArray()
Method B:
1. Create a StringBuilder
2. Append each row to the builder
3. Return builder.split("\n")
Not sure it makes much of a difference, the toArray method is most likely faster as there is less String processing. The split would have to process the entire data with regex; the toArray method would just need to loop over the Collection.
If you amend your method B so that you don't read the file line-by-line into the StringBuilder but use Files.readAllBytes to get the entire file as a String then split you will probably find performance more or less identical.
If you have Java 8:
final Path path = /*some path*/
final String[] lines = Files.lines(path).toArray(String[]::new);
Note, your method A can be improved by using Files.readAllLines:
final String[] lines = Files.readAllLines(path, StandardCharsets.UTF_8).
toArray(new String[0]);
There's probably very little difference. I don't think you're working with very large files anyway, so it shouldn't matter. You can profile the different ways if you really are interested in it, but the choice you make is quite irrelevant.
I would go with the ArrayList way if it was my choice, since concatenation just for splitting afterwards seems redundant.
Wait, if you read a file in this format:
A
B
C
D
E
F
Why not just read it and save in the same time?
Something like:
BufferedReader bufferedReader = new BufferedReader(new FileReader("test.txt"));
List<String> lines = new ArrayList<String>();
for (String line; (line = bufferedReader.readLine()) != null; )
{
lines.add(line);
}
System.out.println(lines);
And you will have [A, B, C, D, E, F, G] in your lines List.
lines.toArray(); --- About "not be added while processing" i need for info.