RFR: 8281223: Improve the API documentation of HttpRequest.Builder::build to state that the default implementation provided by the JDK returns immutable objects.

[Daniel Fuchs]

On Tue, 15 Feb 2022 14:05:16 GMT, Conor Cleary <ccleary at openjdk.org> wrote:

> As described in the title, this is a simple change to the `HttpRequest.Builder::build` method to highlight that an immutable and reusable instance of an `HttpRequest` is created when this method is invoked. This is done by adding an `@implSpec` Javadoc Tag (details on `@implSpec` given [here](https://openjdk.java.net/jeps/8068562)). 
> 
> The detail added under the `@implSpec` Tag is similar to that provided at the interface-level Javadoc for Builder.
> 
> Please also review the CSR for this change: https://bugs.openjdk.java.net/browse/JDK-8281833

src/java.net.http/share/classes/java/net/http/HttpRequest.java line 297:

> 295:          * @implSpec Returns a new {@code HttpRequest} each time it is
> 296:          * invoked. Once built, the HttpRequest is immutable and can be
> 297:          * sent multiple times.

Looks fine to me. Maybe "This method returns ..." would more appropriate for an `@implSpec`. Also the second mention of `HttpRequest` should also have `{@code }` around it.

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PR: https://git.openjdk.java.net/jdk/pull/7479