RFR: 5108778 Too many instances of java.lang.Boolean created in Java application(core-libs) (original) (raw)

Sebastian Sickelmann sebastian.sickelmann at gmx.de
Fri Oct 9 19:23:08 UTC 2015

On 10/09/2015 08:58 PM, Stuart Marks wrote:

On 10/9/15 4:16 AM, Aleksey Shipilev wrote:

Please note that "static final Boolean myBool = new Boolean(true).booleanValue()" is a spec-recommended way to avoid binary incompatibilities caused by conditional compilation. See JLS 13.4.9. Therefore, deprecating Boolean constructors is a spec issue as well. Well, not "recommended" :-) but point well taken. From JLS 13.4.9: I didn't know that there is a recommended workaround for this in the JLS, but maybe it is in the wrong chapter. Chapter "13 Binary Compatibility" is fine for the first part of "13.4.9 |final| Fields and |static| Constant Variables". But the workaround for should be documented in a chapter that handles the conditional compilation. The only place i could find is the end of "14.21. Unreachable Statements"

We note, but do not recommend, that if a field of primitive type of an interface may change, its value may be expressed idiomatically as in: boolean debug = new Boolean(true).booleanValue(); The bit about conditional compilation is with regard to constant expressions. The goal here is to get a boolean value into the initializer of a field, but to have that initializer not be a constant expression. I think that Boolean.valueOf(true).booleanValue()

I have tried it. And it works as described on primitive types. So a

static final Boolean myBool = new Boolean(true).booleanValue()

is not needed because-

static final Boolean myBool = true

works too due to autoboxing and implicitly changing to

static final Boolean myBool = Boolean.valueOf(true)

would be sufficient for this and avoids using the constructor. And i think i would use Boolean.TRUE.booleanValue() to do the trick on booleans. The valueOf works best with every other Wrapper-Type. I'll file a bug on the JLS for this. What is the Bug-Number. Maybe i can watch and comment on this.

Thanks

Thanks! s'marks

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