Why does Type inference not work in the Processing editor?

Processing
21

Now, if we simply use final List<Double> list = new ArrayList<>();
Rather than final List<? extends Double> list = new ArrayList<>();
Then list.add(d); works as it should: :sunglasses:

import java.util.List;
import java.util.ArrayList;

public class Test {
  public final List<Double> list = new ArrayList<>();
  public final double d = Math.random();

  public Test() {
    list.add(d); // now it finally works!
  }

  @Override public String toString() {
    return list.toString();
  }

  @SafeVarargs public static final void main(final String... args) {
    System.out.println(new Test());
  }
}
22

Just found out that final List<? super Double> list = new ArrayList<>(); works too! :partying_face:

Somehow only final List<? extends Double> list = new ArrayList<>(); is problematic. :confused:

23

Oh yeah, I realized I confused these two right there.
Of course, for super I can put Doubles in as I like.
And on the other hand, for extends I can’t put in Doubles for sure but what you get is definitely a Double or inheriting from it.
So
List<? extends Double> L = new ArrayList<>();
Double d = L.get(0);
compiles, though would throw an error at runtime with this exact code only.

24

I guess I’ll just add it here because it’s from the same corner, but lambda expressions don’t work either.
Lambda expressions are allowed only at source level 1.8 or above
:frowning:

25

That’s right. I suspect a rule of thumb about the current syntax is “most of 7, bits of 8” – and unfortunately lambdas are not a part of 8 that got got. GoToLoop has been pining for adding lambdas to Processing for … maybe a decade…? Another rule of thumb is the more complex or abstract a Java feature is the less likely it is to have been prioritized for Antlr pre-processor handling. A few things were acquired essentially “for free” because the preprocessor didn’t have to be changed, just pass them through.