How is this meaningfully different from the Java 8 Streams API? It seems to be functionally equivalent right up to lazy evaluation, just with SQL vocabulary (select, where, etc) instead of functional vocabulary (map, filter, etc).
Java streams read data from spinning rust and then does the selection in RAM. LINQ can send the "where" to the RDBMS and the RDBMS can use an index/btree lookup to read just the data needed where java streams would read umpty megabytes.
I don't know whether the JINQ people plan to write a good query generator. But if I were the maintainer, my plan would definitely be to focus on the API first and only then work on optimal backend implementation(s).
List<ProductDisplayInfo> list = Arrays
.asList(products)
.stream()
.filter(p -> p.getCategory() == 2 || p.getCategory() == 5 && isProductUnderDiscount(p))
.map(p -> new ProductDisplayInfo(p))
.collect(Collectors.toList());
For fun, you can further reduce the size of the code above (and IMO, make it clearer), but using `Arrays.stream(product)` and a method reference for the `map`:
List<ProductDisplayInfo> list = Arrays
.stream(products)
.filter(p -> p.getCategory() == 2 || p.getCategory() == 5 && isProductUnderDiscount(p))
.map(ProductDisplayInfo::new)
.collect(Collectors.toList());