JAVA Array Index Problems

Question

I am not experienced wit Arrays and I am getting this error in the debug console:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1 at com.company.SortTextFile.main(SortTextFile.java:28)

I've been looking in internet for how other people handle this included here in StackOverflow but I can't seem to understand why is it happening. I am trying to have this program get the input from a text file of multiple columns with 20 lines like this: Eduardo 15 3.9 30000 And then using collection.sort to sort it using its id. I am aware the arrays are 0-index however I don't know if I would need to specify the array size.

import java.io.*;
import java.util.ArrayList;
import java.util.Collections;

import static java.lang.Double.*;

public class SortTextFile {
  public static void main(String[] args) throws IOException {
    // Creating BufferedReader object to read the input text file

    BufferedReader reader = new BufferedReader(new FileReader(
        "C:\\Users\\miche\\OneDrive\\Documentos\\University\\Algorithms\\Project\\StudentData.txt"));

    // Creating ArrayList to hold Student objects

    var studentRecords = new ArrayList<Student>();

    // Reading Student records one by one

    String currentLine = reader.readLine();

    while (currentLine != null) {
      String[] studentDetail = currentLine.split("\\s+");

      String name = studentDetail[0];
      int age = Integer.valueOf(studentDetail[1]);
      double GPA = valueOf(studentDetail[2]);
      int id = Integer.valueOf(studentDetail[3]);

      // Creating Student object for every student record and adding it to
      // ArrayList

      studentRecords.add(new Student(name, age, GPA, id));

      currentLine = reader.readLine();
    }

    // Sorting ArrayList studentRecords based on marks

    Collections.sort(studentRecords, new idCompare());

    // Creating BufferedWriter object to write into output text file

    BufferedWriter writer = new BufferedWriter(new FileWriter(
        "C:\\C:\\Users\\miche\\OneDrive\\Documentos\\University\\Algorithms\\Project\\output.txt"));

    // Writing every studentRecords into output text file

    for (Student student : studentRecords) {
      writer.write(student.name);

      writer.write(" " + student.age);

      writer.write(" " + student.GPA);

      writer.write(" " + student.id);

      writer.newLine();
    }

    // Closing the resources

    reader.close();

    writer.close();
  }
}

I made a Student class to compare the IDs.

public class Student extends SortTextFile {
String name;
int id;
int age;
double GPA;

public Student(String name, int id, double age, double GPA) {
    this.name = name;
    this.id = id;
    this.age = (int) age;
    this.GPA = GPA;
  }
}
//idCompare Class to compare the marks
class idCompare implements Comparator<Student> {
@Override
public int compare(Student s1, Student s2) {
    return s2.id - s1.id;}
}

Edit 1: The text file just follows a format of Name/Age/GPA/ID: Chipaldo 25 3.5 29000

Eduardo 15 3.9 30000 

Ricardo 23 3.8 18000

Anthony 24 3.9 19000

Lombardo 29 2.0 22000

Romina 28 2.1 23000

Alex 25 3.1 13000

Sofia 21 2.2 24000

Vexler 24 2.2 25000

Albert 19 3.2 14000

John 24 3.0 15000

Melchor 14 2.9 16000

Bernardo 21 4.0 17000

Diego 19 2.1 26000

Miguelangel 25 2.0 27000

Edit 3: I managed to printout the Output in a new file. It sorted it based on age and not ID for some reason. Thank you for your help. I am going to try implement and Binary Insertion Sort to this program instead of doing Collection.sort Thanks.

If possible please be as detailed as possible with any suggestion. English is not my main language & I am slow at this. Thank you in advance

Could you please post some of your file contents? (StudentData.txt) — mettleap
– mettleap, Commented Nov 29, 2018 at 17:28

Speakjava · Accepted Answer · 2018-11-29 17:32:16Z

1

The message simply means that you have an array that only has 1 element in it and you are trying to access array element 2. This is one of those weird things in computer science (and Java as a language) because we start counting from zero rather than one, i.e. the first element in an array is indexed as studentDetail[0] and the second as studentDetail[1]. This is why you see the rather confusing "Index 1 out of bounds for length 1". The array being returned by currentLine.split(" ") only contains one string, not four, as you are expecting. You need to debug the code to find out why this is happening (from what you've provided this is not possible for someone else to answer).

answered Nov 29, 2018 at 17:32

Speakjava

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1 Comment

JavaBeginner9163 Over a year ago

Thank you very much. I tried debugging the code but I can't seem to find the issue. I added the full code to the post. I've been to solve this for a couple of hours. I added what another comment suggest for the split.string to the currentLine.split to make it accept any space or tab. Any suggestion?

Talik · Accepted Answer · 2018-11-29 17:28:06Z

0

your array seems to only have one entry. check if there is a problem with your string.split(" ")?

answered Nov 29, 2018 at 17:28

Talik

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Saptarshi Basu · Accepted Answer · 2018-11-29 17:38:54Z

0

Use currentLine.split("\\s+"); This means that there may be one or more spaces or tabs or newlines between fields.

What you did will work correctly if and only if the fields are separated by one single space.

For debugging purpose print the length of the array using System.out.println(studentDetail.length);

edited Nov 29, 2018 at 17:38

answered Nov 29, 2018 at 17:32

Saptarshi Basu

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Comments

flopcoder · Accepted Answer · 2018-11-29 17:59:46Z

Try This. Your code you did not closed writer thats why nothing is to in the output file.

 public static void main(String[] args) throws IOException {
        //Creating BufferedReader object to read the input text file

        BufferedReader reader = new BufferedReader(new FileReader("E:\\Projects\\JavaBasics\\src\\data.txt"));

        //Creating ArrayList to hold Student objects
        var studentRecords = new ArrayList<Student>();

        //Reading Student records one by one
        String currentLine = null;
        while ((currentLine = reader.readLine()) != null) {
            if (!currentLine.isEmpty()) {
                System.out.println(currentLine);

                String[] studentDetail = currentLine.split(" ");
                String name = studentDetail[0];
                int age = Integer.valueOf(studentDetail[1]);
                double GPA = Double.valueOf(studentDetail[2]);
                int id = Integer.valueOf(studentDetail[3]);
                studentRecords.add(new Student(name, age, GPA, id));
            }
        }

        //Sorting ArrayList studentRecords based on marks
        Collections.sort(studentRecords, new IdCompare());
        //Creating BufferedWriter object to write into output text file
        BufferedWriter writer = null;

        try {
            writer = new BufferedWriter(new FileWriter(new File("E:\\Projects\\JavaBasics\\src\\dataout.txt")));

            //Writing every studentRecords into output text file

            for (Student student : studentRecords) {
                System.out.println("Sorted :: " + student.name);
                writer.write(student.name);
                writer.write(" " + student.age);
                writer.write(" " + student.GPA);
                writer.write(" " + student.id);
                writer.newLine();
            }
        } finally {
            writer.close();
        }
    }

Thank you. I did this and a couple of changes and it printed the output. Only issue is that it sorted it based on age not the id, so thats what I am trying to fix now. Thank you

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