Setting a value for a constant in Java after declaration

Question

For simplicity I will use a basic example.

If I am using a record (struct) in my Java program like so:

public class Store{
  class Product{
    final int item1;
    final int item2;
    final int item3;
  }

and I create a constructor for my class that will take values to represent the value of each item:

  public Store(int[] elements) {

     Product x = new Product();
     x.item1 = elements[0];
     x.item2 = elements[1];
     x.item3 = elements[2];
  }
}

The compiler gives me two errors:

"The blank final field item1 may not have been initialized

"The final field cannot be assigned"

I understand that we can not re-assign values to constants, but is there a way to assign values to uninitialized constants?

Answer 1

The only way is to assign such values in the constructor, so you would need to add a constructor to your structure class:

class Product{

    Product(double item1, double item2, double item3) {
        this.item1 = item1;
        this.item2 = item2;
        this.item3 = item3;
    }


    final double item1;
    final double item2;
    final double item3;
}

And then use it in the rest of your code:

public Store(int[] elements) {

    Product x = new Product(elements[0], elements[1], elements[2]);

}