How to import a file into multiple ArrayList in Java?

Question

Java beginner here, please be patient. So I need to import a txt file that looks like this

A

Germany

India

B

Vietnam

China

and the program will need to compare the country that the user typed then determine whether it belongs to group A or B and return the group. I have been told to use ArrayList. At the moment my code looks like

public class regionCountry
{
   public String region;
   public ArrayList <String> countryList;
} 

public class destination
{
   public static void main (String [] args)
   {
      ArrayList<regionCountry> rc = new ArrayList<regionCountry>;
   }
}

but I still have no idea what to do. Any help will be much appreciated.

Have you read documentation on reading text files? Start with that and show some code on how far you get, then we will help you. — ruthless, Sep 12 '14 at 05:29
this [link](http://stackoverflow.com/questions/2788080/reading-a-text-file-in-java) will get you started. — Ker p pag, Sep 12 '14 at 05:33
If you're talking about the scanner and new File() then yes. It looks something like Scanner c = new Scanner(new File("c:/myfile.txt")); My question is how to determine if the country belongs to the specific group as there are multiple countries in one group. — bisonsausage, Sep 12 '14 at 05:36
Your naming convention for naming classes is wrong. Use Capitalized. Your code to next reader should be good read. — Pramod S. Nikam, Sep 12 '14 at 05:43

Ruchira Gayan Ranaweera · Answer 1 · 2014-09-12T05:59:29.013

You can follow following steps.

1. Read your file (You can use Scanner)
2. Split data and store them in a `ArrayList`.

Now let's try to work on these.

How to read a file?

 File file=new File("yourFilePath");
 Scanner scanner=new Scanner(file);
 while (scanner.hasNextLine()){
      // now you can get content of file from here.
 }

Then split content and create an instance of your object set region and add country list.

Note:

Use proper naming conversion. change regionCountry to RegionCountry. Class name should start with capital letter.

Make all variables private and add public getters and setters.

Edit: for your comment. How to determine the group and country?

 File file=new File("/home/ruchira/Test.txt");
 Scanner scanner=new Scanner(file);
 RegionCountry regionCountry = null;
 List<RegionCountry> regionCountryList=new ArrayList<>();
 List<String> groupList=new ArrayList<>();
 groupList.add("A");
 groupList.add("B");
 List<String> countryList = null;
  while (scanner.hasNextLine()){
    String line=scanner.nextLine();
    if(!"".equals(line)){
        if(groupList.contains(line.trim())){
         if(regionCountry!=null&&groupList.contains(regionCountry.getRegion())){
             regionCountryList.add(regionCountry);
           }
          regionCountry=new RegionCountry();
          regionCountry.setRegion(line);
          countryList=new ArrayList<>();
          }else {
          countryList.add(line);    // those will never be null in this logic
          regionCountry.setCountryList(countryList);
         }
       }
   }
  regionCountryList.add(regionCountry);// last group you have to take from here.
  System.out.println(regionCountryList);

Out put: (I have override toString() in RegionCountry )

[RegionCountry{region='A', countryList=[Germany, India]}, RegionCountry{region='B', countryList=[Vietnam, China]}]

How to import a file into multiple ArrayList in Java?

1 Answers1