test/jdk/java/util/Optional/BasicDouble.java

*** 30,39 ****
--- 30,41 ----
   */
  
  import java.util.NoSuchElementException;
  import java.util.OptionalDouble;
  import java.util.concurrent.atomic.AtomicBoolean;
+ import java.util.function.DoublePredicate;
+ import java.util.List;
  
  import static org.testng.Assert.*;
  import org.testng.annotations.Test;
  
  public class BasicDouble {
*** 49,58 ****
--- 51,61 ----
          assertFalse(empty.equals(OptionalDouble.of(UNEXPECTED)));
          assertFalse(OptionalDouble.of(UNEXPECTED).equals(empty));
          assertFalse(empty.equals("unexpected"));
  
          assertFalse(empty.isPresent());
+         assertTrue(empty.isEmpty());
          assertEquals(empty.hashCode(), 0);
          assertEquals(empty.orElse(UNEXPECTED), UNEXPECTED);
          assertEquals(empty.orElseGet(() -> UNEXPECTED), UNEXPECTED);
  
          assertThrows(NoSuchElementException.class, () -> empty.getAsDouble());
*** 124,129 ****
--- 127,148 ----
  
      @Test(groups = "unit")
      public void testStreamPresent() {
          assertEquals(OptionalDouble.of(DOUBLEVAL).stream().toArray(), new double[] { DOUBLEVAL });
      }
+ 
+     @Test(groups = "unit")
+     public void testIsEmpty() {
+         OptionalDouble empty = OptionalDouble.empty();
+         assertTrue(empty.isEmpty());
+         OptionalDouble present = OptionalDouble.of(DOUBLEVAL);
+         assertFalse(present.isEmpty());
+         var doubleList = List.of(1.0, 2.0, 3.0, 4.0, 5.0);
+         DoublePredicate isPositiveNumber = x -> x > 0;
+         DoublePredicate isNegativeNumber = x -> x < 0;
+         OptionalDouble positiveNumber = doubleList.stream().mapToDouble(Double::doubleValue).filter(isPositiveNumber).findAny();
+         OptionalDouble negativeNumber = doubleList.stream().mapToDouble(Double::doubleValue).filter(isNegativeNumber).findAny();
+         assertFalse(positiveNumber.isEmpty());
+         assertTrue(negativeNumber.isEmpty());
+     }
+ 
  }