CODEWITHSUNDEEP
javaoop
Johan Ekman
Johan Ekman

Reputation: 3

Accessing an object of a class from another class object

Starting of I want to apologise for my english as I'm not a native speaker. The title might be a bit off since I was not sure how to phrase it but hopefully it will come through once I show my code.

The problem I'm phasing is I want to use the shop class to handle any purchases while storing the money variable on the player class.

Is there any way to access the money integer of the player class without creating an object of the player class in the shop class ?

I was thinking about using a static integer to store the data in but from what I've read online its bad practice to use static datatypes.

public class Beta {

    public static void main(String[] args) {
        Player p1 = new Player("Test");
        Shop s1 = new Shop();

        p1.setMoney(100);
        s1.clerk(p1.getMoney());

    }
}


public class Player {

    private int money;
    private String name;

    public Player(String name) {
        this.name = name;
    }   
    public int getMoney() {
        return money;
    }
    public void setMoney(int x) {
        this.money +=x;
    }
}

public class Shop {

  private int money;

  public void clerk(int x) {
       this.money = x;
       if (this.money >= total) {
           question4 = false;
           System.out.println("Your purchase was successful!");
           if (blue > 0) {
               this.addInventory("Blue", blue);
           }
           if (red > 0) {
               this.addInventory("Red", red);
           }
           if (green > 0) {
               this.addInventory("Green", green);
           }
        }
        else {
            question4 = false;
            System.out.println("Sorry you cant afford that!");
        }       
     }      
   }
}

So I cut down my code to show you only the essential parts. What I want to do is access p1:s money variable from the player class from within the Shop class.

So far I have been passing the variable when calling it from main. Is this the only option I have or can it be accessed in any other way ?

Any help would be much appreciated!

Upvotes: 0

Views: 575

Answers (2)

Tsunoba
Tsunoba

Reputation: 60

I believe the option that follows Object-Oriented Programming principles best is to pass the actual Player in as an argument, instead of just the money.

Basically, passing just the player's money in instead of the player themselves is like just handing your wallet over to the cashier. You wouldn't do that, right?

This way, the clerk can ask the customer if they have enough money by calling player.getMoney(), and the customer can tell them the answer.

After making the purchase, the player can remove the money from their wallet themselves when the clerk asks them to via player.setMoney().

Now, you asked in a comment about "passing the actual player as an argument without creating a new object of the player class." Java passes arguments by value, and all objects' values are simply the address that hold the information for that particular instance.

So for Player p1 in Beta, let's pretend all of p1's information is stored in a block starting at...let's say, address 21343. In this case, the variable p1 only contains that single number, 21343.

Since Java passes by value, then when you call s1.clerk(Player player), the player variable will also contain 21343. Since it's editing the items contained at the same address, you've essentially passed on p1 itself instead of creating a new Player. In short, the clerk and the main method work with the same object.

The fact that Java passes by value is also why passing just the player's money in doesn't adjust it automatically: The money is an int rather than an object. Since it's an int, when you pass it to the clerk, you're just saying "Hey, clerk, this is the amount of money being worked with." But the clerk has no idea who the money belongs to, so while it can take money, or even give it some, it's essentially just setting it down on the counter, and it's the responsibility of the player to pick it up from there when they're done. By passing in the player instead, the clerk knows who the money belongs to because it's actually asking the player how much money they have.

Upvotes: 2

Gus Garrison
Gus Garrison

Reputation: 1

Another potential solution would be to make p1 and s1 static variables in the Beta class. It'd look something like this:

public class Player
{
    public static Player p1;
    public static Shop s1;

    public static void main(String[] args)
    {
        p1 = new Player("Test");
        s1 = new Shop();

        p1.setMoney(100);
        s1.clerk(p1.getMoney());
    }
}

From there, you'd import the Beta class in Shop, then call Beta.p1 in Shop to access p1. Hope this helps!

Upvotes: -1

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