For-each loop won't print the first requested line

Question

ISSUE:

When I run this everything works fine. Let's say that my chosen IDs are: 0001, 0002, 0003, 0004. And their infos: info1, info2, info3, info4. If I pass 0002 in the scanner I get info2. As you'd expect but if I pass in 0001 I'd expect to get info1 but instead I get nothing. I tried this with an array of fixed size 3 and it worked just fine. I changed to an ArrayList because I don't know how long the file would be. Why does this happen?

I'm a newbie in programming so please forgive my lack of knowledge about where to look for these things.

What my program does is, read in a file and add all the rows to an ArrayList and then asks for input from the user, the input should be in the format of xxxx or 4 characters.

The text file I made as an example looks as follows, no extra spaces on the lines:

0001
info1
4
0002
info2
5
0003
info3
9
0004
info4
10
0005
info5
3

The main class:

public class Main {

    public static ArrayList<Gameobject> games = new ArrayList<>();

    public static void main(String[] args) throws IOException {

        Scanner sc = new Scanner(new File("objects.txt"));

        String id, info;
        int amount;

        while(sc.hasNextLine()) {

            id = sc.nextLine();
            info = sc.nextLine();
            amount = Integer.parseInt(sc.nextLine());

            Gameobject s = new Gameobject(id, info, amount);

            games.add(s);
            System.out.println(s.getId());
         }

        sc = new Scanner(System.in);

        info(sc.next());

     }

The info method is as follows.

public static void info(String id){  
    for(Gameobject s : games){    
        if(s.getId().equals(id)){
            System.out.println(s.getInfo());
        }
    }
}

And the class Gameobject

public class Gameobject {

    String id, info;
    int amount;

    Gameobject(String id, String info, int amount) {
        this.id = id;
        this.info = info;
        this.amount = amount;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getInfo() {
        return info;
    }
    public void setInfo(String info) {
        this.info = info;
    }
    public int getAmount() {
        return amount;
    }
    public void setAmount(int amount) {
        this.amount = amount;
    }
}

I did some tests and passed in games.get(0).getId() to the info method and it worked. That got me the ID "0001" from the Gameobject. However just passing in "0001" did not.

Answer 1

I am with Lefteris008 on this one. Check your objects.txt.

Your IDs are Strings and inside your for-loop you compare Gameobject.getId() to a console input.

Having your objects.txt contain the id 0001<space> instead of 0001 is enough for .equals(id) to yield false.

If there is a chance that your input will be malformed, you could try to make your code act more defensive:

// This will remove leading and trailing whitespaces
id = sc.nextLine().trim();

This is just to help you get an idea of how to handle your input data. This is far from production ready.