CODEWITHSUNDEEP
javaarraysarraylistnullpointerexceptionreadfile
SLM
SLM

Reputation: 25

having trouble extracting data from a file, spliting it and storing it into array/arraylist

I have a file that contains information like this: table of the data

The number of lines varies. The professor is using other document to test the program.

I want to extract the long name from this file and print it.

Here is what I have:

public List<String> extractName(List<String> longName)
{
  Data data = new Data();
  Scanner scan = new Scanner(actualFile);
  longName = new List<String>();
  String line = scan.nextLine();

    if(line.contains("---"))
      {
         while(line != null)
      {
         String[] name = line.split(" +");
         longName.add(name[2]);
      }
     data.setLongName(longName);
   }
  return longName;
}

and my main method and one other method:

  public static void main(String[] args) throws FileNotFoundException{
    //process file
      try{
          File actualFile = new File(args[0]);
          System.out.println("File was processed: true");
         }
      catch (ArrayIndexOutOfBoundsException e)
            {
                System.out.println("File was processed: false. Re-enter filename.");
                return;
            }
      Data data = new Data();
      printInfo(data); // error occurs here
  }

  public static void printInfo(Data d){
        for(int i = 0; i < longName.size(); i++) //error occurs here
          System.out.println(longName.get(i));

  }

and my class, in case anyone needs it:

public class Data{

    private List<String> longName;

    public void Data(){}

    public void setLongName(List<String> theLongName){
        longName = theLongName;
    }
    public List<String> getLongName(){
        return longName;
    }
}

But when I run it, I get this error:

Exception in thread "main" java.lang.NullPointerException
    at project2shm.printInfo(project2shm.java:35)
    at project2shm.main(project2shm.java:18)

I am so confused. I labeled where the error occurred in the code. Can anyone help me, please?

Upvotes: 1

Views: 39

Answers (1)

cybersam
cybersam

Reputation: 66989

project2shm.main() never assigns a value to the longName variable used by project2shm.printInfo(). That longName variable is apparently a static variable in the project2shm class.

You did not provide the entire source for project2shm, but it either does not initialize longName, or assigns null to it. In either case, that will cause the NPE that you saw.

Upvotes: 1

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