Combine Singleton + Adapter

Design Patterns/src/adapter/animal/BirdAdapter.java

@@ -2,12 +2,22 @@ package adapter.animal;
 
 public class BirdAdapter implements ToyDuck {
 
-    private final Bird bird;
+    private Bird bird;
+    private static BirdAdapter instance;
 
-    public BirdAdapter(Bird bird) {
+    private BirdAdapter(Bird bird) {
         this.bird = bird;
     }
 
+    public static BirdAdapter getInstance(Bird bird) {
+        if (instance == null) {
+            instance = new BirdAdapter(bird);
+        } else if (!instance.bird.equals(bird)) {
+            instance.bird = bird;
+        }
+        return instance;
+    }
+
     @Override
     public void squeak() {
         bird.makeSound();

Design Patterns/src/adapter/animal/Main.java

@@ -14,7 +14,7 @@ public class Main {
         plasticToyDuck.squeak();
 
         System.out.println("\nBirdAdapter...");
-        ToyDuck birdAdapter = new BirdAdapter(sparrow);
+        ToyDuck birdAdapter = BirdAdapter.getInstance(sparrow);
         birdAdapter.squeak();
 
     }

Design Patterns/src/adapter/animal/tests/BirdAdapterTest.java

@@ -13,7 +13,7 @@ class BirdAdapterTest {
     @Test
     void verifyMakeSoundIsCalled() {
         Bird mockedSparrow = mock(Sparrow.class);
-        ToyDuck birdAdapter = new BirdAdapter(mockedSparrow);
+        ToyDuck birdAdapter = BirdAdapter.getInstance(mockedSparrow);
 
         birdAdapter.squeak();
         verify(mockedSparrow, times(1)).makeSound();