Member Avatar for beforetheyknew

So the program I have is supposed to read from a file take that data (which is split into three parts divided by a space). These Strings need to be read and stored in an appropriate field. Now i dont know how to do this, I've tried with an array as you can see which i think is right but it only stores a single line. Someone told me that i should do that and then have spearate array objects or something? but i dont really know how. Help would be massivley appreciated.

import java.util.Scanner;
import java.io.*;

public class DataRead
{  
    
        private Scanner scan; 
        private String[]arraySplit = null;
    
    public DataRead()     
    {  
     
        arraySplit = new String[100];
        
        try
        {  
            FileReader inputFile = new FileReader(//read file);
            scan = new Scanner(inputFile);    
        }
        catch (FileNotFoundException e)
        {
            System.out.println("FileNotFoundException - Could not find file");
        }
        catch (Exception e)
        {
            System.out.println("Unknown error");
        }   
        
         while(scan.hasNext())  //reads through file while there is more to file
        {
                String line = scan.nextLine();      
                arraySplit = line.split(" ");          
        }
             
    }
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  • Latest Post Latest Post by imclumsy

Dani AI

Generated

Your code is overwriting the same array on every loop, so only the last line survives. Instead of assigning one array per iteration, accumulate each record into a collection (or store columns into separate collections). For three fixed fields per line, three common approaches are: a List<String[]> (each element is a 3-element array), three parallel lists (one per column), or a small POJO (preferred for clarity) and a List<POJO>.

As pointed out, tokenizing is the right idea. Prefer Scanner.next() or reading lines and parsing—StringTokenizer is legacy. If the file really is "three space-separated tokens per record," the simplest robust pattern is to read tokens in groups of three and add a new record for each group.

Example using a tiny Record class and Scanner.next():

static class Record {
    String f1, f2, f3;
    Record(String f1, String f2, String f3) { this.f1 = f1; this.f2 = f2; this.f3 = f3; }
    public String toString() { return f1 + " " + f2 + " " + f3; }
}

List<Record> records = new ArrayList<>();
try (Scanner sc = new Scanner(new File("data.txt"))) {
    while (sc.hasNext()) {
        String a = sc.next();
        if (!sc.hasNext()) break;
        String b = sc.next();
        if (!sc.hasNext()) break;
        String c = sc.next();
        records.add(new Record(a, b, c));
    }
}

Troubleshooting notes:

  • Validate token counts; guard against truncated lines.
  • If fields can contain spaces, use quoted CSV or another delimiter and parse lines accordingly.
  • For very large files, process each record as you read it instead of storing everything in memory.
  • Use try-with-resources (above) so the file is closed even on exceptions.

For : change from reassigning one array each loop to adding a new element to a collection (as shown). That will keep every line’s data instead of just the last.

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Member Avatar for imclumsy

i think you can use a StringTokenizer and use the delimiter of " " to divide the string into three parts and put it in three different fields.
The psedocode would be:
initialize a string tokenizer ---> StringTokenizer scT = new StringTokenizer(name of file being read. delimeter);
while (scT.hasmoreTokens())
field one = scT.next
field two = scT.next
filed three = scT.next

i hope that is something along the lines of what you're looking for...i don't see your whole code so i cannot test it

Member Avatar for imclumsy

sorry its
StringTokenizer scT = new StringTokenizer(name of file being read, delimeter);

you should also probably look at the java api of the StringTokenizer

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