[BAEL-16531] - Move all the existing articles on "optional" under java-optional

core-java-modules/core-java-9-improvements/README.md

@@ -5,7 +5,6 @@ This module contains articles about the improvements to core Java features intro
 ### Relevant Articles:
 
 - [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
-- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
 - [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
 - [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
 - [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/Java9OptionalTest.java

@@ -1,85 +0,0 @@
-package com.baeldung.java9;
-
-public class Java9OptionalTest {
-    @Test
-    public void givenOptionalOfSome_whenToStream_thenShouldTreatItAsOneElementStream() {
-        //given
-        Optional<String> value = Optional.of("a");
-
-        //when
-        List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
-
-        //then
-        assertThat(collect).hasSameElementsAs(List.of("A"));
-    }
-
-    @Test
-    public void givenOptionalOfNone_whenToStream_thenShouldTreatItAsZeroElementStream() {
-        //given
-        Optional<String> value = Optional.empty();
-
-        //when
-        List<String> collect = value.stream().map(String::toUpperCase).collect(Collectors.toList());
-
-        //then
-        assertThat(collect).isEmpty();
-    }
-
-    @Test
-    public void givenOptional_whenPresent_thenShouldExecuteProperCallback() {
-        //given
-        Optional<String> value = Optional.of("properValue");
-        AtomicInteger successCounter = new AtomicInteger(0);
-        AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
-
-        //when
-        value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
-
-        //then
-        assertThat(successCounter.get()).isEqualTo(1);
-        assertThat(onEmptyOptionalCounter.get()).isEqualTo(0);
-    }
-
-    @Test
-    public void givenOptional_whenNotPresent_thenShouldExecuteProperCallback() {
-        //given
-        Optional<String> value = Optional.empty();
-        AtomicInteger successCounter = new AtomicInteger(0);
-        AtomicInteger onEmptyOptionalCounter = new AtomicInteger(0);
-
-        //when
-        value.ifPresentOrElse((v) -> successCounter.incrementAndGet(), onEmptyOptionalCounter::incrementAndGet);
-
-        //then
-        assertThat(successCounter.get()).isEqualTo(0);
-        assertThat(onEmptyOptionalCounter.get()).isEqualTo(1);
-    }
-
-    @Test
-    public void givenOptional_whenPresent_thenShouldTakeAValueFromIt() {
-        //given
-        String expected = "properValue";
-        Optional<String> value = Optional.of(expected);
-        Optional<String> defaultValue = Optional.of("default");
-
-        //when
-        Optional<String> result = value.or(() -> defaultValue);
-
-        //then
-        assertThat(result.get()).isEqualTo(expected);
-    }
-
-    @Test
-    public void givenOptional_whenEmpty_thenShouldTakeAValueFromOr() {
-        //given
-        String defaultString = "default";
-        Optional<String> value = Optional.empty();
-        Optional<String> defaultValue = Optional.of(defaultString);
-
-        //when
-        Optional<String> result = value.or(() -> defaultValue);
-
-        //then
-        assertThat(result.get()).isEqualTo(defaultString);
-    }
-}