Reading a text file to a HashMap in Java

Question

I have a text file in the following format:

Student1 Marks
Student2 Marks

The first column is the key.

This is what I have tried so far

Scanner scanner = new Scanner(new FileReader("marks.txt"));

    HashMap<String,Integer> map = new HashMap<String,Integer>();

    while (scanner.hasNextLine()) {
        String[] columns = scanner.nextLine().split("\t");

        map.put(columns[0],columns[1]);
    }

    System.out.println(map);        


}

it looks like if you split just on " " rather than "\t" it should work — ControlAltDel
– ControlAltDel, Commented May 6, 2015 at 15:31
also, you are putting a String value when it should be an Integer — MikeB
– MikeB, Commented May 6, 2015 at 15:32
@ControlAltDel: Since the split takes a regex, then I think that \s+ would work better. — npinti
– npinti, Commented May 6, 2015 at 15:32

Vasco Lameiras · Accepted Answer · 2015-05-06 15:35:47Z

1

Just make sure you parse the marks and that the values are indeed tab separated, otherwise code worked for me right away

    Scanner scanner = new Scanner(new FileReader("marks.txt"));

    HashMap<String,Integer> map = new HashMap<String,Integer>();

    while (scanner.hasNextLine()) {
        String[] columns = scanner.nextLine().split("\t");

        map.put(columns[0],Integer.parseInt(columns[1]));
    }

    System.out.println(map);

answered May 6, 2015 at 15:35

Vasco Lameiras

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3 Comments

Tavo Over a year ago

Or juts do split("\\s+"), which will split by any number of whitespaces.

user3402248 Over a year ago

It gives me an error:** The method put(String, Integer) in the type HashMap<String,Integer> is not applicable for the arguments (String, String)**

Vasco Lameiras Over a year ago

@user3402248 That is the error I got when I ran your code. Just use Integer.parseInt on the second parameter of map.put() and the error will be fixed

Community · Accepted Answer · 2017-05-23 12:21:52Z

0

(With a little help from the comments) your code should be reading into the HashMap already, so i assume your problem is printing the HashMap after reading it in.

System.out.println(map) only gives you the representation of the map object. I suggest reading this: Convert HashMap.toString() back to HashMap in Java

To print all elements of that HasMap you could iterate over it, like shown here: Iterate through a HashMap

edited May 23, 2017 at 12:21

CommunityBot

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answered May 6, 2015 at 15:43

Tanix

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