ArrayList and .add() method in java

Question

I am writing a program that has to read information from file and put them into ArrayList, I think my code is right but Eclipse is saying :The method add(int, String[]) in the type ArrayList<String[]> is not applicable for the arguments (int, String) about account.add(0, x[0]); in my code.

My code:

public static void main(String args[]) {

    ArrayList<String[]> account = new ArrayList<>();
    String line = "";
    try {
        FileReader fr=new FileReader("information.txt");

        Scanner information = new Scanner(fr);
        while (information.hasNext()) {

            // find next line
            line = information.next();

            String x[]=line.split("-");
            account.add(0, x[0]);
            account.add(0, x[1]);
            account.add(0, x[2]);
        }
    }
}

Do you want each element in the list to be the data for one line of your file, or do you want each line to be transformed into three elements? — Pete Kirkham
– Pete Kirkham, Commented Jun 15, 2018 at 12:00
You have a try block without a catch (or a finally block or a resource initialisation). — khelwood
– khelwood, Commented Jun 15, 2018 at 12:02

ikos23 · Accepted Answer · 2018-06-15 12:06:43Z

4

This is the signature of the method you're using :

public void add(int index, E element) { ... }

You have ArrayList<String[]>, so the method expects an array of Strings as a second param. And what you provide is just a String (element from the array).

Try this:

String x[]=line.split("-");
account.add(0, x); // because x is actually an array

Or you can use it like that:

account.add(x);

If you still need to put elements from the array into your list like you do here:

account.add(0, x[0]);
account.add(0, x[1]);
account.add(0, x[2]);

try to change ArrayList<String[]> to ArrayList<String>.

And just a comment that has nothing to do with your question :) This is a better practice:

// use interface List in the left part :)
List<String[]> account = new ArrayList<>();

Happy hacking :)

edited Jun 15, 2018 at 12:06

answered Jun 15, 2018 at 12:00

ikos23

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Comments

Andrew · Accepted Answer · 2018-06-15 11:57:55Z

0

You should to just write account.add(x[0]); For example:

ArrayList<String> arrayList = new ArrayList<>();
arrayList.add("smth");

answered Jun 15, 2018 at 11:57

Andrew

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