Multiple object in array (java)

Question

I want to create objects using the result from Scanner and add them to an array.

However, each time I ask for user input for the second time, it just overwrites the first object.

How can I add multiple objects to the array?

Here's my code:

public void ajoutadd() {
    int i=0;
    boolean boucle=true;
    while(i!=2){
        Scanner thegame = new Scanner(System.in);
        System.out.print("name: \n");
        String jname = lejeu.nextLine();
        System.out.print(jname);
        Scanner qty = new Scanner(System.in);
        System.out.print("qty \n");
        int jqty = qty.nextInt();
        Scanner cat = new Scanner(System.in);
        System.out.print("cat: \n");
        String categ = cat.nextLine();
        Scanner price = new Scanner(System.in);
        System.out.print("price: \n");
        int jprice = price.nextInt();
        Game agame = new Game(jname,jqty,categ,jprice);
        System.out.print(unjeu.Nom);

        // creating the array to contain the game(s)
        ArrayList<Game> thegame = new ArrayList<Game>(); 

        thegame.add(new Game(jname,jqty,categ,jprice));

        // actually only display 1 object that is overwritten
        // each time after the loop
        System.out.println(thegame);

        i=i++;
    }
}

Simba · Accepted Answer · 2014-12-15 04:12:35Z

2

Your loop is not actually overwriting the first value. It is just creating a new ArrayList every time you loop through.

You should create one ArrayList and continously add to it.

ex.

ArrayList<Game> games = new ArrayList<Game>();
while(...) {
   ...
   games.add(...);
   ...
}

Couple notes:

You do not have to create a new Scanner for every scan you can just use the same one (Also initialize it outside the loop like the array list).
i=i++ could just be i++, i++ increments the variable i, it is different than i + 1. It is equivalent to i = i + 1.
It is good practice to use the List interface for the ArrayList variable so that your code will work the same regardless of which List implementation you use.

edited Dec 15, 2014 at 4:12

answered Dec 15, 2014 at 4:07

Simba

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1 Comment

Phil_oneil Over a year ago

thanks a lot.Good advice and answer.I created only one scanner like you said,however theres something wrong at the cat and price input,when the compiler reach these,it prints cat: and price: and its like if the price: was going over cat: without letting time to input the cat String? I dont know if you understand what i mean.Like I cant input cat,it immediatly jump to price?

Elliott Frisch · Accepted Answer · 2014-12-15 04:05:12Z

1

Create one Scanner outside the loop and one List instance (and I suggest you use the interface). Like,

public void ajoutadd() {
    int i = 0;
    boolean boucle = true;
    Scanner thegame = new Scanner(System.in);
    List<Game> thegame = new ArrayList<>();
    while (i != 2) {
        System.out.print("name: \n");
        String jname = thegame.nextLine();
        System.out.print(jname);
        System.out.print("qty \n");
        int jqty = thegame.nextInt();
        System.out.print("cat: \n");
        String categ = thegame.nextLine();
        System.out.print("price: \n");
        int jprice = thegame.nextInt();
        Game agame = new Game(jname, jqty, categ, jprice);
        System.out.print(unjeu.Nom);
        thegame.add(new Game(jname, jqty, categ, jprice));
        System.out.println(thegame);
        i++; // <-- not i = i++;
    }
}

answered Dec 15, 2014 at 4:05

Elliott Frisch

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2 Comments

Phil_oneil Over a year ago

And how do I return the arraylist to be able to use it in other class?

Elliott Frisch Over a year ago

Change public void ajoutadd() { to public List<Game> ajoutadd() { and add a return thegame; after your while loop. Also, you should probably ask a new question (and do some research) on your own.

Panther · Accepted Answer · 2014-12-15 06:52:47Z

1

Move initialization of list outside the loop. Currently, you are creating list object everytime in loop. Hence losing the reference to existing one.

public  ArrayList<Game> ajoutadd() {
    int i=0;
    boolean boucle=true;
     ArrayList<Game> thegame = new ArrayList<Game>(); 
    while(i!=2){
    Scanner thegame = new Scanner(System.in);
    System.out.print("name: \n");
    String jname = lejeu.nextLine();
    System.out.print(jname);
    Scanner qty = new Scanner(System.in);
    System.out.print("qty \n");
    int jqty = qty.nextInt();
    Scanner cat = new Scanner(System.in);
    System.out.print("cat: \n");
    String categ = cat.nextLine();
    Scanner price = new Scanner(System.in);
    System.out.print("price: \n");
    int jprice = price.nextInt();
    Game agame = new Game(jname,jqty,categ,jprice);
    System.out.print(unjeu.Nom);
   //creating the array to contain the game(s)
    thegame.add(new Game(jname,jqty,categ,jprice));
   each time after the loop


    i++;

    }
  System.out.println(thegame); 
  return  thegame;


}

edited Dec 15, 2014 at 6:52

answered Dec 15, 2014 at 4:04

Panther

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6 Comments

Phil_oneil Over a year ago

And how do I return the arraylist to be able to use it in other class?

Panther Over a year ago

changed the return type to Arraylist and returned the list. Now you get this value in calling method. Kindly accept the answer or upvote if it works for you.

Phil_oneil Over a year ago

I did what you told me too,however when I try to call it in other methods, like public void disp(){ System.out.print(thegame);} the game doesnt get recognized...?

Panther Over a year ago

While calling from other method save the value in other variable and print them. ArrayList<Game> game = ajoutadd(); System.out.println(game);. thegame has method level scope so will not be recognized outside method but you can get returned value in variables

Panther Over a year ago

This is because this variable in scope of method , but we added return statement so that we get value in calling method. disp(){ ArrayList<Game> game = ajoutadd() ; System.out.println(game); } .

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