Initializing an array using a method - Java

Question

I have a text file with n amount of athletes names, each name on a new line, and the number of athletes is written as an int on the first line of the text file. The code i have written so far reads the text file, and using scanner and creates an array with all the data (Athletes names). What I wondering is, is it possible to use a method to create a separate array for each athlete (I will later fill these with data on scores/ performance). I cannot initialize these before the text file is scanned as the number of athletes will not yet be known.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;


public class TextScanner {

  private static void readFile(String fileName) {
    try {
      List<String> distance = new ArrayList<String>();
      File file = new File(fileName);
      Scanner scanner = new Scanner(file);
      while (scanner.hasNext()) {
          distance.add(scanner.next());
      }
      scanner.close();
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    }
  }

 public static void main(String[] args) {

    readFile(args[0]);
  }
}

Very new to Java, so I apologise. I have looked around and cant seem to find any information. Thanks

may this help you ; stackoverflow.com/questions/12777274/dynamic-arraylist-in-java — newuserua_ext
– newuserua_ext, Commented Mar 12, 2015 at 7:01
You can create a new type/class to represent your Athlete info and add to list or a Map... so later you can again set properties of those objects as required.. — Xavier DSouza
– Xavier DSouza, Commented Mar 12, 2015 at 7:06
then you can use HashMap<String,List> and arraylist is dynamic. — Prashant
– Prashant, Commented Mar 12, 2015 at 7:07
@newuserua_ext Thanks, yeh i saw that, but i think most of the answers misunderstood his question, and were focusing on adding elements to an existing array. — user3636636
– user3636636, Commented Mar 12, 2015 at 7:16
No Most of users doesn't misunderstood , they are trying to tell you the Correct way of doing it ! Everytime the way which solves your problem is not the correct and only way! — Neeraj Jain
– Neeraj Jain, Commented Mar 12, 2015 at 7:18

Neeraj Jain · Accepted Answer · 2015-03-12 07:06:30Z

4

Yes it is possible , but Array has certain limitation as it can not expand and collapse dynamically

Try this way

Create a Class Athelete having attributes you want to keep for athelete

Say

Class Athelete{

private String name;
private Integer age;
private String skill;

// then Getters and Setters for each of these
}

and create a Map

Map<String,Athelete> // having `name` as Key and `athelete object` as value.

Now Read from file and create Athelete Object and add it to Map.

Person p=new Person();
p.setName=nameFromFile();
// also set further attributes
map.put(p.getName,p);

answered Mar 12, 2015 at 7:06

Neeraj Jain

7,7308 gold badges36 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Vince Over a year ago

@XavierDSouza Should have posted it as an answer

Rohit · Accepted Answer · 2015-03-12 07:16:32Z

Since Java is object oriented language think objects and in your case its seems to be Athlete, Score and Performance

public class Athlete {
    String name;
    List<Score> scores = new ArrayList<Score>();
    List<Performance> performances = new ArrayList<Performance>();
}

public class Score {
    String score
}

public class Performance {
    int performnce
}

So List<String> distance = new ArrayList<String>(); this will become List<Athlete> Athletes = new ArrayList<Athlete>();

For each record in the file create Athlete object and store the name in name instance variable. As you get the scores and performances for each particular Athlete updte the Athlete objects already created above.

Update

As other commentator have pointed out using a Map rather than Listwould be suitable. for eg Map<String, Athlete> athletes = new HashMap<String, Athlete>(); This way updating later on receiveing the score s and performances becomes easier. Also, scores and performances are List as an Athlete could have multiple score and performnces.

Michael Kazarian · Accepted Answer · 2015-03-12 07:35:52Z

2

You can create class Athlete:

class Athlete{
   String name;
   int score;
   Athlete(String name){
      this.name = name;
   }
   int getScore(){return score;}
   void setScore(int score){ this.score = score}
}

and insert instances of Athlete into array or List:

List<Athlete> distance = new ArrayList<>();
distance.add(new Athlete('Some name'));

UPD: if you use Java7 consider java.nio.file.Files instead Scanner for read small files. I think readAllLines method will useful for you.

edited Mar 12, 2015 at 7:35

answered Mar 12, 2015 at 7:06

Michael Kazarian

4,4921 gold badge23 silver badges27 bronze badges

2 Comments

user3636636 Over a year ago

Thank you! Just to clarify, if i were to run a for loop, or something similar, i could continually create new objects for each athlete using the class? Appreciate your help

Michael Kazarian Over a year ago

@user3636636 Create new instance in loop it usual OOP (and java as OOP language) pattern. You can find it in either book about java.

Ravikiran butti · Accepted Answer · 2015-03-12 07:00:42Z

0

you can first add all the data (Athletes names) to a list and later call list.toArray(new Athlete[list.size()]); this will get you your required Array

answered Mar 12, 2015 at 7:00

Ravikiran butti

1,6682 gold badges13 silver badges18 bronze badges

Comments

pkalinow · Accepted Answer · 2015-03-12 07:03:02Z

0

Sure, you can create an array for each record from the file. The method signature would look like e.g.

String[] readAthleteData() {...}

However, using collections like ArrayList is usually more convenient than arrays.

answered Mar 12, 2015 at 7:03

pkalinow

1,7471 gold badge17 silver badges46 bronze badges

Collectives™ on Stack Overflow

Initializing an array using a method - Java

5 Answers 5

1 Comment

Comments

2 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

Comments

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related