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Thread: referencing variables from multiple instances of a class?

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    Default referencing variables from multiple instances of a class?

    Hello,

    I'm new to Java, and reading Intro to Java Programming for Dummies, and I was just wanting to clarify something about creating and referring to objects. This is my first post, so please forgive any formatting blunders..

    Here is the code (from pg. 333):
    import java.util.Scanner;
     
    class ProcessPurchasesss {
     
       public static void main(String args[]) {
          Scanner myScanner = new Scanner(System.in);
          Purchase aPurchase;
     
          for (int count = 0; count < 3; count++) {
             aPurchase = new Purchase();
              System.out.print("Amount: ");
             aPurchase.amount = myScanner.nextDouble();
             System.out.print("Taxable? (true/false) ");
             aPurchase.taxable = myScanner.nextBoolean();
     
             if (aPurchase.taxable) {
                aPurchase.total = aPurchase.amount * 1.05;
             } else {
                aPurchase.total = aPurchase.amount;
             }
     
             System.out.print("Total: ");
             System.out.println(aPurchase.total);
             System.out.println();
          }
       }
    }

    My question is -> if one creates multiple objects all assigned to the same variable (in this case 'aPurchase') how does one refer to each individual object variable? so if I referred to aPurchase.total, I'd only get the last assigned value right?

    many thanks!
    Nick


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    Default Re: referencing variables from multiple instances of a class?

    Your understanding is correct. As with any variable, it will store the last item assigned to it.

    Multiple distinct objects can be stored in arrays or other collections. The array is likely the first you'll learn, so I'll use that as an example. The statement:

    Purchase[] purchases = new Purchases[10];

    creates an array called 'purchases' that is sized to store 10 Purchase objects.

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    Default Re: referencing variables from multiple instances of a class?

    It's not so much that multiple objects are assigned to the same variable, but rather that each individual object created has it's own unique variable values and such.

    Like Greg said, you can use an array to create multiple purchase objects and access them like that. To access any object within the array Greg wrote above, you would write:

    int selectedIndex = 0; //Which ever purchase object you would like to refer too from the array
     
    int newPurchaseTotal = purchases[selectedIndex].total; //ex, if you wanted to store it in a new variable

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