> However, many Java language features are not supported by Java Card (in particular types char, double, float and long; the transient qualifier; enums; arrays of more than one dimension; finalization; object cloning; threads). Further, some common features of Java are not provided at runtime by many actual smart cards (in particular type int, which is the default type of a Java expression; and garbage collection of objects).
[EDIT] But I am not arguing with the overarching argument that Java proper can run efficiently on very constrained devices. It all depends on the implementation.
Not Java, not even close. JavaCard is an extremely stripped-down version of Java. I've used it and it feels like C.
From https://en.wikipedia.org/wiki/Java_Card#Java_Card_vs._Java:
> However, many Java language features are not supported by Java Card (in particular types char, double, float and long; the transient qualifier; enums; arrays of more than one dimension; finalization; object cloning; threads). Further, some common features of Java are not provided at runtime by many actual smart cards (in particular type int, which is the default type of a Java expression; and garbage collection of objects).
[EDIT] But I am not arguing with the overarching argument that Java proper can run efficiently on very constrained devices. It all depends on the implementation.