CODEWITHSUNDEEP
javaloopsinput
coinbird
coinbird

Reputation: 1217

Reading a text file with a loop JAVA

My program reads a set of data, processes it, prints stuff, and then is supposed to continue on to the next set of data, until there is no more. My program works if I give it one set of data, but I get an error when I add a second.

In my BlueJ window it says 

java.lang.ArrayIndexOutOfBoundsException: 15

The error in the terminal says:

java.lang.ArrayIndexOutOfBoundsException: 15
at Prog4.read_votes(Prog4.java:97)
at Prog4.main(Prog4.java:38)

38 is in the main method:

p4.read_votes(stdin, votesArray);

97 is:

votes[i] = stdin.nextInt();

and it's in the read_votes method:

public void read_votes(Scanner stdin, int votes[])
{
 //for (int i = 0; i < votes.length; i++)
 //   votes[i] = stdin.nextInt();  

 int i = 0;

  while (stdin.hasNextInt())
  {
     votes[i] = stdin.nextInt();
     i++;
  }
}

Here is my class and main method:

public class Prog4
{
int mostVotes = 0;
int mostVotesIndex = 0;
int fewestVotes = 0;
int fewestVotesIndex = 0;

public static void main(String args[]) throws Exception
{
  //Scanner stdin = new Scanner(System.in);
  Scanner stdin = new Scanner(new File("test.txt"));
  int num_votes, num_candidates, election_num = 1;



  System.out.println("Welcome to Prog4!\n");
  Prog4 p4 = new Prog4();

  while (stdin.hasNextLine())
  {

     System.out.println("Results for election " + election_num);

     num_candidates = stdin.nextInt();
     String[] candidateArray = new String[num_candidates];
     p4.read_candidates(stdin, candidateArray);

     num_votes = stdin.nextInt();
     int[] votesArray = new int[num_votes];
     p4.read_votes(stdin, votesArray);


     p4.read_votes(stdin, votesArray);
     System.out.println("Total votes: " + votesArray.length);
     p4.process_highest_vote_getter(candidateArray, votesArray);
     p4.process_lowest_vote_getter(candidateArray, votesArray);
     p4.process_winner(candidateArray, votesArray);
  }

System.out.println("Done. Normal termination of Prog4.");
}

Here is the data being read from the text file:

4
Owen
Jack
Scott
Robbie
15 0 1 1 2 3 1 0 0 0 0 1 2 2 1 1

2
Erik
Martin
10 0 1 0 1 0 1 0 0 0 1

EDIT:

I changed the read_votes method to:

public void read_votes(Scanner stdin, int votes[])
{
  for (int i = 0; i < votes.length && stdin.hasNextInt(); i++)
     votes[i] = stdin.nextInt();  
}

It gives the correct output for the first set of data, but I get an error when it starts doing the second set. There error reads: 

java.util.InputMismatchException

and it's on this line in the main method: num_candidates = stdin.nextInt();

Upvotes: 3

Views: 11877

Answers (3)

amald
amald

Reputation: 346

You are reading votes twice in your code.

Your code

int[] votesArray = new int[num_votes];
 **p4.read_votes(stdin, votesArray);**


 **p4.read_votes(stdin, votesArray);**

When it happens reading formatted data will be broken.

And I have done following changes to your code. then it'll work fine.

public void read_votes(Scanner stdin, int votes[])
{
    //for (int i = 0; i < votes.length; i++)
    //   votes[i] = stdin.nextInt();


    for(int i = 0; i < votes.length; ++i)
    {
        votes[i] = stdin.nextInt();
    }
}

public void read_candidates(Scanner stdin, String candidates[])
{
    //for (int i = 0; i < votes.length; i++)
    //   votes[i] = stdin.nextInt();

    stdin.nextLine();
    for(int i = 0; i < candidates.length; ++i)
    {
        candidates[i] = stdin.nextLine();
    }
}

Upvotes: 3

Stefan Fandler
Stefan Fandler

Reputation: 1141

Change the loop in read_votes() to:

while(i < votes.length && stdin.hasNextInt()) {
    // ...
}

Your loop reads the number(s) from the next line.

Upvotes: 0

chrylis -cautiouslyoptimistic-
chrylis -cautiouslyoptimistic-

Reputation: 77167

You're continuing to read nextInts as long as the input has them. In particular, you're reading the number 2 (indicating the number of candidates for the next election) and trying to count it as a vote for election 1.

Instead, iterate from 0 to votes.length in your read_votes method; if you're guaranteed valid input (or it's acceptable to throw exceptions on bad input), then you don't need to continually check hasNextInt().

Upvotes: 0

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