Java 10 allows implicit typing for local variables. You can get a quick refresher here.
Fast forward 6 months, Java 11 will be supporting local variable syntax support for Lambda Parameters in an implicitly typed lambda expression.
Here is an example from the spec:
(var x, var y) -> x.process(y)
With this support, annotations can be added to local variables as they require full type.
(@NotNull var x, @Nullable var y) -> x.process(y)
Expanding the example from my earlier post. Lines #17 and #57 shows this support in action.
| import org.jetbrains.annotations.NotNull; | |
| import java.util.Comparator; | |
| import java.util.function.ToLongFunction; | |
| import java.util.stream.Stream; | |
| public class RideProviderTest { | |
| @FunctionalInterface | |
| private interface RideProvider { | |
| long getFareEstimate(String type); | |
| } | |
| public static void main(String[] args) { | |
| // implicitly typed lambda expression | |
| ToLongFunction<RideProvider> lyftProvider = (@NotNull var provider) –> provider.getFareEstimate("Lyft"); | |
| var lyft = new RideProvider() { | |
| @Override | |
| public long getFareEstimate(String type) { | |
| var estimated_cost_cents_max = 0; | |
| switch (type) { | |
| case "Line": | |
| estimated_cost_cents_max = 3307; | |
| break; | |
| case "Lyft": | |
| estimated_cost_cents_max = 7306; | |
| break; | |
| case "Plus": | |
| estimated_cost_cents_max = 12451; | |
| break; | |
| case "Premier": | |
| estimated_cost_cents_max = 17562; | |
| break; | |
| case "Lux": | |
| estimated_cost_cents_max = 23624; | |
| break; | |
| case "Lux SUV": | |
| estimated_cost_cents_max = 25879; | |
| break; | |
| } | |
| return estimated_cost_cents_max; | |
| } | |
| }; | |
| long lyftFare = lyftProvider.applyAsLong(lyft); | |
| // implicitly typed lambda expression | |
| ToLongFunction<RideProvider> uberProvider = (@NotNull var provider) –> provider.getFareEstimate("uberX"); | |
| var uber = new RideProvider() { | |
| @Override | |
| public long getFareEstimate(String type) { | |
| var estimated_cost_cents_max = 0; | |
| switch (type) { | |
| case "POOL": | |
| estimated_cost_cents_max = 7000; | |
| break; | |
| case "EXPRESS POOL": | |
| estimated_cost_cents_max = 7000; | |
| break; | |
| case "uberX": | |
| estimated_cost_cents_max = 9200; | |
| break; | |
| case "WAV": | |
| estimated_cost_cents_max = 9200; | |
| break; | |
| case "ASSIST": | |
| estimated_cost_cents_max = 9200; | |
| break; | |
| case "uberXL": | |
| estimated_cost_cents_max = 14800; | |
| break; | |
| case "SELECT": | |
| estimated_cost_cents_max = 20900; | |
| break; | |
| case "SUV": | |
| estimated_cost_cents_max = 30600; | |
| break; | |
| } | |
| return estimated_cost_cents_max; | |
| } | |
| }; | |
| long uberFare = uberProvider.applyAsLong(uber); | |
| // compare the futures for best fare estimate | |
| Stream.of(lyftFare, uberFare) | |
| . | |
| min(Comparator.comparing(i –> i)) | |
| . | |
| ifPresent(estimated_cost_cents_max –> System.out.println("$" + estimated_cost_cents_max / 100)); | |
| } | |
| } |
Java 11 is releasing next month! IntelliJ IDEA 2018.2 has already added support for this feature.
