RFR: 8279598: Provide adapter from RandomGenerator to Random [v16]

[Stuart Marks]

On Fri, 11 Mar 2022 01:25:28 GMT, Yasser Bazzi <duke at openjdk.java.net> wrote:

>> Hi, could i get a review on this implementation proposed by Stuart Marks, i decided to use the https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/random/RandomGenerator.html interface to create the default method `asRandom()` that wraps around the newer algorithms to be used on classes that do not accept the new interface.
>> 
>> Some things to note as proposed by the bug report, the protected method next(int bits) is not overrided and setSeed() method if left blank up to discussion on what to do with it.
>> 
>> Small test done on https://gist.github.com/YShow/da678561419cda8e32fccf3a27a649d4
>
> Yasser Bazzi has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Merge branch 'randomwrapper' of https://github.com/YShow/jdk.git into randomwrapper
>  - Remove atomicLong allocation and override next(int) method to throw UOE

A small spec change is necessary; please make it here, and I'll copy it into the CSR.

src/java.base/share/classes/java/util/Random.java line 98:

> 96:         private RandomWrapper(RandomGenerator randomToWrap) {
> 97:             super(null);
> 98:             this.generator = Objects.requireNonNull(randomToWrap);

Can remove `requireNonNull` here; see other comments. At your option, add a comment saying that `randomToWrap` must not be null. This is easy to verify since there's only one caller elsewhere in this file.

src/java.base/share/classes/java/util/Random.java line 320:

> 318:      * @param generator the {@code RandomGenerator} calls are delegated to
> 319:      * @return the delegating {@code Random} instance
> 320:      */

Need to add

    @throws NullPointerException if generator is null

src/java.base/share/classes/java/util/Random.java line 327:

> 325:         return new RandomWrapper(generator);
> 326:     }
> 327: 

I'd suggest adding

    Objects.requireNonNull(generator)

as the first line of this method. In fact if null is passed, NPE is thrown already, as the `instanceof` will be false and then the `RandomWrapper` constructor will throw NPE. However, verifying this requires a bit of hunting around and some flow analysis to determine this. Might as well make the null check explicit at the top of this method. The now-redundant check can be removed from `RandomWrapper`.

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PR: https://git.openjdk.java.net/jdk/pull/7001