Prepare for forthcoming @Nullable annotations on Optional.orElseGet.

Soon, nullness checkers will know that `orElseGet` can return `null`... but not be smart enough to know that it can't return `null` _here_.

RELNOTES=n/a
PiperOrigin-RevId: 597579395

guava/src/com/google/common/collect/Streams.java

@@ -953,7 +953,7 @@ T get() {
   public static OptionalInt findLast(IntStream stream) {
     // findLast(Stream) does some allocation, so we might as well box some more
     java.util.Optional<Integer> boxedLast = findLast(stream.boxed());
-    return boxedLast.map(OptionalInt::of).orElseGet(OptionalInt::empty);
+    return boxedLast.map(OptionalInt::of).orElse(OptionalInt.empty());
   }
 
   /**
@@ -971,7 +971,7 @@ public static OptionalInt findLast(IntStream stream) {
   public static OptionalLong findLast(LongStream stream) {
     // findLast(Stream) does some allocation, so we might as well box some more
     java.util.Optional<Long> boxedLast = findLast(stream.boxed());
-    return boxedLast.map(OptionalLong::of).orElseGet(OptionalLong::empty);
+    return boxedLast.map(OptionalLong::of).orElse(OptionalLong.empty());
   }
 
   /**
@@ -989,7 +989,7 @@ public static OptionalLong findLast(LongStream stream) {
   public static OptionalDouble findLast(DoubleStream stream) {
     // findLast(Stream) does some allocation, so we might as well box some more
     java.util.Optional<Double> boxedLast = findLast(stream.boxed());
-    return boxedLast.map(OptionalDouble::of).orElseGet(OptionalDouble::empty);
+    return boxedLast.map(OptionalDouble::of).orElse(OptionalDouble.empty());
   }
 
   private Streams() {}