Question

Documentation for the constructor new Boolean(boolean value) in Java states:

Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance.

If so, why is this constructor public and not deprecated? Is there ever a good reason to use this constructor instead of Boolean.valueOf()?

Answer 1

valueOf() only got added in Java 1.4, so it would appear that the constructors exist for backwards compatibility.

This ticket explains the reasons for not deprecating the constructors:

Due to the disruption deprecating an API can have, currently an API
has to be "actively hazardous" to be deprecated, like Thread.stop.
While the use this constructor is certainly ill-advised, it doesn’t
rise (or sink) to the standard of hazardousness to be deprecated in
the JDK. In the future we may add a "denigration" facility to mark
API elements that aren’t quite so bad that they should be deprecated,
but shouldn’t be used in most cases. This constructor would be a good
candidate for denigration.

I can’t think of a realistic scenario where using Boolean constructors would be the best way to do something useful.