Array of booleans

[Maurizio Cimadamore]

On 18/03/2021 15:04, Remi Forax wrote:
> Hi everybody,
> It seems it's not possible to create a VarHandle on array of booleans
>    static final VarHandle BOOLEAN_HANDLE = ofSequence(ofValueBits(8, LITTLE_ENDIAN))
>          .varHandle(boolean.class, sequenceElement());
>
> Is there a reason for that ?
>
>  From the JVM POV, a boolean is stores on 8 bits and in the bytecode baload/bastore can load/store from either an array of booleans or an array of bytes.

If I'm not mistaken, that representation is not specfied? E.g. hotspot 
uses it, but there is latitude? Quoting from VM spec:

```

In Oracle’s Java Virtual Machine implementation, |boolean| arrays in the 
Java programming language are encoded as Java Virtual Machine |byte| 
arrays, using 8 bits per |boolean| element.
```

Note "Oracle" :-)

That was the rationale for omitting booleans. It should be possible to 
use custom adapters if you want to speculate on the shape of e.g. a 
boolean array - but we'd prefer not to add VM impl-specific assumption - 
or that was the idea at least.

Maurizio

>
> regards,
> Rémi