Stream confusion

[Archie Cobbs]

Argh, sorry I pasted the wrong example. The Widget fields "color" and
"weight" are supposed to NOT be final:

@@ -5,8 +5,8 @@

 public class Widget {

-    private final Color color;
-    private final int weight;
+    private Color color;
+    private int weight;

     public Widget(Color color, int weight) {
         this.color = color;

The question remains the same - is the program deterministic?

-Archie

On Wed, Nov 22, 2023 at 10:06 AM Archie Cobbs <archie.cobbs at gmail.com>
wrote:

> I have an API design question about Streams, but instead of asking the
> question outright I thought I'd ask it indirectly with a simple example.
>
> The Javadoc for Stream opens with this example:
>
>         int sum = widgets.stream()
>                       .filter(w -> w.getColor() == RED)
>                       .mapToInt(w -> w.getWeight())
>                       .sum();
>
> OK, looks reasonable - we're computing the sum of the weights of all the
> red widgets.
>
> Here's the question: Is the following program deterministic?
>
> import java.awt.*;
> import java.util.function.*;
> import java.util.stream.*;
> import static java.awt.Color.*;
>
> public class Widget {
>
>     private final Color color;
>     private final int weight;
>
>     public Widget(Color color, int weight) {
>         this.color = color;
>         this.weight = weight;
>     }
>
>     public Color getColor() {
>         return this.color;
>     }
>
>     public int getWeight() {
>         return this.weight;
>     }
>
>     public static int totalRedWeight(Widget... widgets) {
>         return Stream.of(widgets)
>                 .filter(w -> w.getColor() == RED)
>                 .mapToInt(w -> w.getWeight())
>                 .sum();
>     }
>
> // Test method
>
>     public static void main(String[] args) {
>         final Widget w1 = new Widget(RED, 123);
>         final Widget w2 = new Widget(BLUE, 456);
>         final int total = Widget.totalRedWeight(w1, w2);
>         System.out.println("Total red weight = " + total);
>     }
> }
>
> -Archie
>
> --
> Archie L. Cobbs
>


-- 
Archie L. Cobbs
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