How to join multiple single arrays into one large single array

Question

So I gathered tokens from multiple lines of a text file and put those tokens into an array called tokens. With this code.

    scanner = new Scanner(file);
        while (scanner.hasNextLine()) {
            if ((line = scanner.nextLine()).charAt(0) != '#') {
                tokens = line.split(",");
            }
        }

(Its all in a try catch block)

I need to put all of those String tokens into a single array, how would I do this. My new array is stringTokens [] = new String [countLines *4].

The while loop redefines the elements in tokens with each iteration, how do I save those old elements in stringTokens and add the new elements tokens will get into stringTokens as well.

That's not compressing, that's joining arrays http://stackoverflow.com/questions/80476/how-to-concatenate-two-arrays-in-java — m0skit0, Jan 26 '15 at 20:10
Also you might consider using List instead, it will make your life much easier. — m0skit0, Jan 26 '15 at 20:12

score 1 · Answer 1 · answered Jan 26 '15 at 20:13

1

You can use an ArrayList<String> for that, and when you need it as array, you can convert it to one:

ArrayList<String> list = new ArrayList<>();
scanner = new Scanner(file);
while (scanner.hasNextLine()) {
    if ((line = scanner.nextLine()).charAt(0) != '#') {
        for(String s : line.split(",")) {
            list.add(s);
        }
    }
}
stringTokens = list.toArray(new String[0]);

answered Jan 26 '15 at 20:13

MinecraftShamrock

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yeah @minecraftshamrock is correct, you can use Lists here, they are dynamic and can be appended – Santhosh Jan 26 '15 at 20:30

score 0 · Answer 2 · answered Jan 26 '15 at 20:13

You should look into using ArrayLists. They are essentially mutable arrays, with no specified size (the array "grows"* as you add elements.) and adding each token to your list of strings.

ArrayList<String> stringTokens = new ArrayList<String>();

...
for(String s : line.split(",")) {
        stringTokens.add(s);
}

*Capacity doubles when needed.

How to join multiple single arrays into one large single array

2 Answers2