Initialize array of objects from text files

Question

I have a program where I need to store users information, and add users. To make it persistent, the program reads all the users data and initializes an array of users upon launch, then saves the information before it closes. Here's my user class:

class User {
    String name;
    int val = -1;
    int oldVal = -1;

    public User(String n){
        try{
             BufferedReader dataReader = new BufferedReader(new FileReader("/Users/" + n));
             name = dataReader.readLine();
             val = Integer.parseInt(dataReader.readLine());
             oldVal = Integer.parseInt(dataReader.readLine());
        } catch (Exception e){}
    }

This class reads from files in /users, following the format name.txt

 John
 90
 100

My core class looks like this:

import java.io.BufferedReader;
import java.io.FileReader;

class Core{
    public static void main (String[] args){
        int numUsers = -1;
        BufferedReader nameReader = null;
        User[] users = null;

        try {
            nameReader = new BufferedReader(new FileReader("Users/users.txt"));
            numUsers = Integer.parseInt(nameReader.readLine());
            users = new User[numUsers];

            for (int i = 0; i < numUsers; i++){
                users[i] = new User(nameReader.readLine());
            }
        } catch (Exception e) {
            System.out.println("Something went wrong. Aborting!");
            System.exit(1);
        }
        for (int i = 0; i < numUsers; i++){
            System.out.println("User " + users[i].getName() + "\n Val:" + users[i].getVal() + "\n oldVal: " + users[i].getOldVal());
        }
    }
}

But running core returns:

User null
val: -1
oldVal: -1

for every user. What is the problem? Is the system I've made viable, or do I need to change the foundation of my program entirely?

(EDIT to change tags)

I guess an exception occurs in your constructor, but due to this line catch (Exception e){}, you'll ignore that. Write e.printStackTrace() into that catch block to see the exception. And if you get one, please edit your question and post the stacktrace here. — Tom
– Tom, Commented Oct 4, 2014 at 14:06
@tom I get a compile time error: "Cannot find symbolm, symbol: printStacktrace() location: variable e of type exception" Odd.EDIT: capitalization error, oops. — LilSweden
– LilSweden, Commented Oct 4, 2014 at 14:09
because I had a typo in it. The correct spelling is printStackTrace() (uppercase T). I edited the first comment. — Tom
– Tom, Commented Oct 4, 2014 at 14:11
@tom I was specifying the files as a path. Adding '+ ".txt"' should fix it, checking now. EDIT: I also needed to get rid of the slash before "Users". — LilSweden
– LilSweden, Commented Oct 4, 2014 at 14:12
Don't forget to read chiastic-securitys answer. His remark is correct. — Tom
– Tom, Commented Oct 4, 2014 at 14:14

chiastic-security · Accepted Answer · 2014-10-04 14:24:18Z

1

Your core is looking for a file in the relative path Users/. Your other class is looking in the absolute path /Users/.

Your textual description says you want /users/ (lower case). On some systems, this will be different again.

I suspect this is causing the problem, or at least part of it.

Looks like what you really want is a relative path, and a .txt on the end:

BufferedReader dataReader = new BufferedReader(new FileReader("Users/" + n + ".txt"));

edited Oct 4, 2014 at 14:24

answered Oct 4, 2014 at 14:07

chiastic-security

20.5k4 gold badges43 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

LilSweden Over a year ago

The additional slash before should not be there, as the path is supposed to be relative. The .txt extension is also missing. I'm unable to mark my own answer, so if you could edit yours to include this I'd be grateful! (and thanks for answering!)

LilSweden · Accepted Answer · 2014-10-04 14:15:32Z

0

 BufferedReader dataReader = new BufferedReader(new FileReader("/Users/" + n));

Should be

 BufferedReader dataReader = new BufferedReader(new FileReader("Users/" + n + ".txt"));

Notice the removal of the extra forward slash and the addition of the .txt extension.

answered Oct 4, 2014 at 14:15

LilSweden

6451 gold badge7 silver badges15 bronze badges

Collectives™ on Stack Overflow

Initialize array of objects from text files

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related