jsedding commented on PR #2457:
URL: https://github.com/apache/jackrabbit-oak/pull/2457#issuecomment-3204673616
Just for fun, this implementation would be `null`-safe. The trick is to use
the `ref` object as a `null`-marker.
However, it might lead to `computeOnce` getting called more than once when
called concurrently. It may be possible to add a guard against this, but I
don't think it's worthwhile.
```
public static <T> Supplier<@Nullable T> memoize(final Supplier<@Nullable
T> computeOnce) {
return new Supplier<>() {
final AtomicReference<Object> ref = new
AtomicReference<>(computeOnce);
@Override
@SuppressWarnings( "unchecked")
public @Nullable T get() {
Object o = ref.updateAndGet(prev ->
Objects.requireNonNullElseGet(
prev,
() ->
Optional.<Object>ofNullable(computeOnce.get()).orElse(ref)
));
return o == ref ? null : (T) o;
}
};
}
```
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