BAEL4640 Find First with Optional (#10142)

* BAEL4640 Find First with Optional

* BAEL4640 Fixes for review comments

* BAEL4640 Removing blank lines

* BAEL4640 Removing blank lines

* BAEL4640 Changes for 8.3 Optional.flatMap

Co-authored-by: Chirag Dewan <chirag.dewan@ericsson.com>

patterns/design-patterns-behavioral/src/main/java/com/baeldung/nulls/UsingOptional.java

@@ -1,23 +1,50 @@
 package com.baeldung.nulls;
 
+import java.util.List;
 import java.util.Optional;
 
+import static java.util.Collections.emptyList;
+
 public class UsingOptional {
 
-    public Optional<Object> process(boolean processed) {
+    public static final String DEFAULT_VALUE = "Default Value";
 
+    public Optional<Object> process(boolean processed) {
         String response = doSomething(processed);
 
         return Optional.ofNullable(response);
     }
 
-    private String doSomething(boolean processed) {
+    public String findFirst() {
+        return getList().stream()
+            .findFirst()
+            .orElse(DEFAULT_VALUE);
+    }
 
+
+    public Optional<String> findOptionalFirst() {
+        return getList().stream()
+            .findFirst();
+    }
+
+    private List<String> getList() {
+        return emptyList();
+    }
+
+    public Optional<String> optionalListFirst() {
+        return getOptionalList().flatMap(
+                list -> list.stream().findFirst());
+    }
+
+    private Optional<List> getOptionalList() {
+        return Optional.ofNullable(getList());
+    }
+
+    private String doSomething(boolean processed) {
         if (processed) {
             return "passed";
         } else {
             return null;
         }
     }
-
 }

patterns/design-patterns-behavioral/src/test/java/com/baeldung/nulls/UsingOptionalUnitTest.java

@@ -11,32 +11,47 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class UsingOptionalUnitTest {
 
-    private UsingOptional classUnderTest;
+    private UsingOptional dataObject;
 
     @BeforeEach
     public void setup() {
-        classUnderTest = new UsingOptional();
+        dataObject = new UsingOptional();
     }
 
     @Test
     public void whenArgIsFalse_thenReturnEmptyResponse() {
-
+        Optional<Object> result = dataObject.process(false);
-        Optional<Object> result = classUnderTest.process(false);
 
         assertFalse(result.isPresent());
     }
 
     @Test
     public void whenArgIsTrue_thenReturnValidResponse() {
-
+        Optional<Object> result = dataObject.process(true);
-        Optional<Object> result = classUnderTest.process(true);
 
         assertTrue(result.isPresent());
     }
 
     @Test
     public void whenArgIsFalse_thenChainResponseAndThrowException() {
-
+        assertThrows(Exception.class, () -> dataObject.process(false).orElseThrow(() -> new Exception()));
-        assertThrows(Exception.class, () -> classUnderTest.process(false).orElseThrow(() -> new Exception()));
     }
+
+    @Test()
+    void givenEmptyList_whenFindFirst_getDefaultValue() {
+        assertTrue(dataObject.findFirst().equalsIgnoreCase(UsingOptional.DEFAULT_VALUE));
+    }
+
+    @Test()
+    void givenEmptyList_whenFindOptionalFirst_returnsEmptyOptional() {
+        assertFalse(dataObject.findOptionalFirst().isPresent());
+    }
+
+    @Test()
+    void whenOptionalListFirst_returnsEmptyOptional() {
+        assertFalse(dataObject.optionalListFirst().isPresent());
+    }
+
+
+
 }