Cleanup and function references

java-collections-conversions/src/main/java/com/baeldung/convertlisttomap/ConvertListToMapService.java

@@ -6,6 +6,7 @@ import org.apache.commons.collections4.MapUtils;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 public class ConvertListToMapService {
@@ -21,7 +22,7 @@ public class ConvertListToMapService {
     }
 
     public Map<Integer, Animal> convertListAfterJava8(List<Animal> list) {
-        Map<Integer, Animal> map = list.stream().collect(Collectors.toMap(Animal::getId, animal -> animal));
+        Map<Integer, Animal> map = list.stream().collect(Collectors.toMap(Animal::getId, Function.identity()));
         return map;
     }
 

java-collections-conversions/src/test/java/com/baeldung/convertcollectiontoarraylist/CollectionToArrayListUnitTest.java

@@ -53,14 +53,14 @@ public class CollectionToArrayListUnitTest {
 
         verifyShallowCopy(srcCollection, newList);
     }
-    
+
     /**
      * Section 5. Deep Copy
      */
     @Test
     public void whenUsingDeepCopy_thenVerifyDeepCopy() {
         ArrayList<Foo> newList = srcCollection.stream()
-          .map(foo -> foo.deepCopy())
+          .map(Foo::deepCopy)
           .collect(toCollection(ArrayList::new));
 
         verifyDeepCopy(srcCollection, newList);
@@ -83,13 +83,13 @@ public class CollectionToArrayListUnitTest {
      * @param a
      * @param b 
      */
-    private void verifyShallowCopy(Collection a, Collection b) {
+    private void verifyShallowCopy(Collection<Foo> a, Collection<Foo> b) {
         assertEquals("Collections have different lengths", a.size(), b.size());
         Iterator<Foo> iterA = a.iterator();
         Iterator<Foo> iterB = b.iterator();
         while (iterA.hasNext()) {
             // use '==' to test instance identity
-            assertTrue("Foo instances differ!", iterA.next() == iterB.next());
+            assertSame("Foo instances differ!", iterA.next(), iterB.next());
         }
     }
     
@@ -98,7 +98,7 @@ public class CollectionToArrayListUnitTest {
      * @param a
      * @param b 
      */
-    private void verifyDeepCopy(Collection a, Collection b) {
+    private void verifyDeepCopy(Collection<Foo> a, Collection<Foo> b) {
         assertEquals("Collections have different lengths", a.size(), b.size());
         Iterator<Foo> iterA = a.iterator();
         Iterator<Foo> iterB = b.iterator();
@@ -106,7 +106,7 @@ public class CollectionToArrayListUnitTest {
             Foo nextA = iterA.next();
             Foo nextB = iterB.next();
             // should not be same instance
-            assertFalse("Foo instances are the same!", nextA == nextB);
+            assertNotSame("Foo instances are the same!", nextA, nextB);
             // but should have same content
             assertFalse("Foo instances have different content!", fooDiff(nextA, nextB));
         }

java-collections-conversions/src/test/java/com/baeldung/convertiteratortolist/ConvertIteratorToListServiceUnitTest.java

@@ -23,7 +23,7 @@ public class ConvertIteratorToListServiceUnitTest {
     Iterator<Integer> iterator;
 
     @Before
-    public void setUp() throws Exception {
+    public void setUp() {
         iterator = Arrays.asList(1, 2, 3)
             .iterator();
     }
@@ -31,7 +31,7 @@ public class ConvertIteratorToListServiceUnitTest {
     @Test
     public void givenAnIterator_whenConvertIteratorToListUsingWhileLoop_thenReturnAList() {
 
-        List<Integer> actualList = new ArrayList<Integer>();
+        List<Integer> actualList = new ArrayList<>();
 
         // Convert Iterator to List using while loop dsf
         while (iterator.hasNext()) {
@@ -44,7 +44,7 @@ public class ConvertIteratorToListServiceUnitTest {
 
     @Test
     public void givenAnIterator_whenConvertIteratorToListAfterJava8_thenReturnAList() {
-        List<Integer> actualList = new ArrayList<Integer>();
+        List<Integer> actualList = new ArrayList<>();
 
         // Convert Iterator to List using Java 8
         iterator.forEachRemaining(actualList::add);