Add Maybe.stream()

CHANGELOG

@@ -6,6 +6,7 @@ CHANGELOG
 
 * Add `Result`
 * Moved `Maybe` to `net.kemitix.mon.maybe.Maybe`
+* Add `Maybe.stream()`
 
 0.6.0
 -----

src/main/java/net/kemitix/mon/maybe/Just.java

@@ -30,6 +30,7 @@ import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 /**
  * A Maybe where a value is present.
@@ -91,4 +92,9 @@ final class Just<T> implements Maybe<T> {
     public void orElseThrow(final Supplier<Exception> e) {
         // do not throw
     }
+
+    @Override
+    public Stream<T> stream() {
+        return Stream.of(value);
+    }
 }

src/main/java/net/kemitix/mon/maybe/Maybe.java

@@ -28,6 +28,7 @@ import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 /**
  * A value that may or may not be present.
@@ -143,4 +144,10 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
     @SuppressWarnings("illegalthrows")
     void orElseThrow(Supplier<Exception> e) throws Exception;
 
+    /**
+     * Converts the Maybe into either a single value stream or and empty stream.
+     *
+     * @return a Stream containing the value or nothing.
+     */
+    Stream<T> stream();
 }

src/main/java/net/kemitix/mon/maybe/Nothing.java

@@ -26,6 +26,7 @@ import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 /**
  * A Maybe where no value is present.
@@ -72,4 +73,9 @@ final class Nothing<T> implements Maybe<T> {
     public void orElseThrow(final Supplier<Exception> e) throws Exception {
         throw e.get();
     }
+
+    @Override
+    public Stream<T> stream() {
+        return Stream.empty();
+    }
 }

src/test/java/net/kemitix/mon/MaybeTest.java

@@ -1,22 +1,20 @@
 package net.kemitix.mon;
 
 import net.kemitix.mon.maybe.Maybe;
+import org.assertj.core.api.WithAssertions;
 import org.junit.Test;
 
 import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Predicate;
+import java.util.stream.Stream;
 
 import static net.kemitix.mon.maybe.Maybe.just;
 import static net.kemitix.mon.maybe.Maybe.maybe;
 import static net.kemitix.mon.maybe.Maybe.nothing;
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatCode;
-import static org.assertj.core.api.Assertions.assertThatNullPointerException;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
-public class MaybeTest {
+public class MaybeTest implements WithAssertions {
 
     private static <T> Predicate<T> eq(final T value) {
         return v -> Objects.equals(value, v);
@@ -112,4 +110,20 @@ public class MaybeTest {
         assertThatThrownBy(() -> nothing().orElseThrow(IllegalStateException::new)).isInstanceOf(
                 IllegalStateException.class);
     }
+
+    @Test
+    public void justToStream() {
+        //when
+        final Stream<Integer> stream = just(1).stream();
+        //then
+        assertThat(stream).containsExactly(1);
+    }
+
+    @Test
+    public void nothingToStream() {
+        //when
+        final Stream<Object> stream = nothing().stream();
+        //then
+        assertThat(stream).isEmpty();
+    }
 }