BAEL-1072 Difference between Proxy, Decorator, Adapter, and Bridge Patterns (#2635)

* Changes as per last review. Changed method names so that they look more idiomatic.

* Updated pattern, changed method names and test cases

core-java/src/main/java/com/baeldung/designpatterns/adapter/AdapterPatternDriver.java

@@ -5,16 +5,16 @@ import static com.baeldung.designpatterns.util.LogerUtil.LOG;
 public class AdapterPatternDriver {
     
     public static void main(String args[]) {
-        LuxuryCars bugattiVeyron = new BugattiVeyron();
-        LuxuryCarsAdapter bugattiVeyronAdapter = new LuxuryCarsAdapterImpl(bugattiVeyron);
-        LOG.info("Bugatti Veyron Super Sport's top speed is " + bugattiVeyronAdapter.speedInKMPH() + " Kmph.");
+    	Movable bugattiVeyron = new BugattiVeyron();
+    	MovableAdapter bugattiVeyronAdapter = new MovableAdapterImpl(bugattiVeyron);
+        LOG.info("Bugatti Veyron Super Sport's top speed is " + bugattiVeyronAdapter.getSpeed() + " Kmph.");
 
-        LuxuryCars mcLaren = new McLaren();
-        LuxuryCarsAdapter mcLarenAdapter = new LuxuryCarsAdapterImpl(mcLaren);
-        LOG.info("McLaren F1 top speed is " + mcLarenAdapter.speedInKMPH() + " Kmph.");
+        Movable mcLaren = new McLaren();
+        MovableAdapter mcLarenAdapter = new MovableAdapterImpl(mcLaren);
+        LOG.info("McLaren F1 top speed is " + mcLarenAdapter.getSpeed() + " Kmph.");
 
-        LuxuryCars astonMartin = new AstonMartin();
-        LuxuryCarsAdapter astonMartinAdapter = new LuxuryCarsAdapterImpl(astonMartin);
-        LOG.info("McLaren F1 top speed is " + astonMartinAdapter.speedInKMPH() + " Kmph.");
+        Movable astonMartin = new AstonMartin();
+        MovableAdapter astonMartinAdapter = new MovableAdapterImpl(astonMartin);
+        LOG.info("McLaren F1 top speed is " + astonMartinAdapter.getSpeed() + " Kmph.");
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/adapter/AstonMartin.java

@@ -1,8 +1,8 @@
 package com.baeldung.designpatterns.adapter;
 
-public class AstonMartin implements LuxuryCars {
+public class AstonMartin implements Movable {
     @Override
-    public double speedInMPH() {
+    public double getSpeed() {
         return 220;
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/adapter/BugattiVeyron.java

@@ -1,8 +1,8 @@
 package com.baeldung.designpatterns.adapter;
 
-public class BugattiVeyron implements LuxuryCars {
+public class BugattiVeyron implements Movable {
     @Override
-    public double speedInMPH() {
+    public double getSpeed() {
         return 268;
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/adapter/LuxuryCars.java

@@ -1,5 +0,0 @@
-package com.baeldung.designpatterns.adapter;
-
-public interface LuxuryCars {
-    public double speedInMPH();
-}

core-java/src/main/java/com/baeldung/designpatterns/adapter/LuxuryCarsAdapter.java

@@ -1,5 +0,0 @@
-package com.baeldung.designpatterns.adapter;
-
-public interface LuxuryCarsAdapter {
-    public double speedInKMPH();
-}

core-java/src/main/java/com/baeldung/designpatterns/adapter/McLaren.java

@@ -1,8 +1,8 @@
 package com.baeldung.designpatterns.adapter;
 
-public class McLaren implements LuxuryCars {
+public class McLaren implements Movable {
     @Override
-    public double speedInMPH() {
+    public double getSpeed() {
         return 241;
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/adapter/Movable.java

@@ -0,0 +1,6 @@
+package com.baeldung.designpatterns.adapter;
+
+public interface Movable {
+    // returns speed in MPH 
+    double getSpeed();
+}

core-java/src/main/java/com/baeldung/designpatterns/adapter/MovableAdapter.java

@@ -0,0 +1,6 @@
+package com.baeldung.designpatterns.adapter;
+
+public interface MovableAdapter {
+    // returns speed in KMPH 
+    double getSpeed();
+}

core-java/src/main/java/com/baeldung/designpatterns/adapter/MovableAdapterImpl.java

@@ -1,15 +1,15 @@
 package com.baeldung.designpatterns.adapter;
 
-public class LuxuryCarsAdapterImpl implements LuxuryCarsAdapter {
-    private LuxuryCars luxuryCars;
+public class MovableAdapterImpl implements MovableAdapter {
+    private Movable luxuryCars;
     
-    public LuxuryCarsAdapterImpl(LuxuryCars luxuryCars) {
+    public MovableAdapterImpl(Movable luxuryCars) {
         this.luxuryCars = luxuryCars;
     }
 
     @Override
-    public double speedInKMPH() {
-        double mph = luxuryCars.speedInMPH();
+    public double getSpeed() {
+        double mph = luxuryCars.getSpeed();
         return convertMPHtoKMPH(mph);
     }
     

core-java/src/main/java/com/baeldung/designpatterns/bridge/Blue.java

@@ -1,12 +1,8 @@
 package com.baeldung.designpatterns.bridge;
 
-import static com.baeldung.designpatterns.util.LogerUtil.LOG;
-
 public class Blue implements Color {
-
     @Override
-    public void fillColor() {
-        LOG.info("Color : Blue");
+    public String fill() {
+        return "Color is Blue";
     }
-
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/BridgePatternDriver.java

@@ -5,10 +5,10 @@ public class BridgePatternDriver {
     public static void main(String[] args) {
         //a square with red color
         Shape square = new Square(new Red());
-        square.drawShape();
+        System.out.println(square.draw());
         
         //a triangle with blue color
         Shape triangle = new Triangle(new Blue());
-        triangle.drawShape();
+        System.out.println(triangle.draw());
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/Color.java

@@ -1,5 +1,5 @@
 package com.baeldung.designpatterns.bridge;
 
 public interface Color {
-    public void fillColor();
+    String fill();
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/Red.java

@@ -1,12 +1,10 @@
 package com.baeldung.designpatterns.bridge;
 
-import static com.baeldung.designpatterns.util.LogerUtil.LOG;
-
 public class Red implements Color {
 
     @Override
-    public void fillColor() {
-        LOG.info("Color : Red");
+    public String fill() {
+        return "Color is Red";
     }
 
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/Shape.java

@@ -7,5 +7,5 @@ public abstract class Shape {
         this.color = color;
     }
     
-    abstract public void drawShape();
+    abstract public String draw();
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/Square.java

@@ -1,7 +1,5 @@
 package com.baeldung.designpatterns.bridge;
 
-import static com.baeldung.designpatterns.util.LogerUtil.LOG;
-
 public class Square extends Shape {
 
     public Square(Color color) {
@@ -9,8 +7,7 @@ public class Square extends Shape {
     }
 
     @Override
-    public void drawShape() {
-        LOG.info("Square drawn. ");
-        color.fillColor();
+    public String draw() {
+        return "Square drawn. " + color.fill();
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/bridge/Triangle.java

@@ -1,7 +1,5 @@
 package com.baeldung.designpatterns.bridge;
 
-import static com.baeldung.designpatterns.util.LogerUtil.LOG;
-
 public class Triangle extends Shape {
 
     public Triangle(Color color) {
@@ -9,8 +7,7 @@ public class Triangle extends Shape {
     }
 
     @Override
-    public void drawShape() {
-        LOG.info("Triangle drawn. ");
-        color.fillColor();
+    public String draw() {
+        return "Triangle drawn. "+ color.fill();
     }
 }

core-java/src/main/java/com/baeldung/designpatterns/decorator/ChristmasTree.java

@@ -1,5 +1,5 @@
 package com.baeldung.designpatterns.decorator;
 
 public interface ChristmasTree {
-    public String decorate();
+    String decorate();
 }

core-java/src/main/java/com/baeldung/designpatterns/proxy/ExpensiveObject.java

@@ -1,5 +1,5 @@
 package com.baeldung.designpatterns.proxy;
 
 public interface ExpensiveObject {
-    public void process();
+    void process();
 }

core-java/src/test/java/com/baeldung/designpatterns/AdapterPatternIntegrationTest.java

@@ -6,15 +6,25 @@ import org.junit.Test;
 
 import com.baeldung.designpatterns.adapter.AstonMartin;
 import com.baeldung.designpatterns.adapter.BugattiVeyron;
-import com.baeldung.designpatterns.adapter.LuxuryCarsAdapterImpl;
 import com.baeldung.designpatterns.adapter.McLaren;
+import com.baeldung.designpatterns.adapter.Movable;
+import com.baeldung.designpatterns.adapter.MovableAdapter;
+import com.baeldung.designpatterns.adapter.MovableAdapterImpl;
 
 public class AdapterPatternIntegrationTest {
     @Test
-    public void givenLuxuryCarsAdapter_WhenConvertingMPHToKMPH_thenSuccessfullyConverted() {
-        assertEquals(new LuxuryCarsAdapterImpl(new BugattiVeyron()).speedInKMPH(), 431.30312, 0.00001);
-        assertEquals(new LuxuryCarsAdapterImpl(new McLaren()).speedInKMPH(), 387.85094, 0.00001);
-        assertEquals(new LuxuryCarsAdapterImpl(new AstonMartin()).speedInKMPH(), 354.0548, 0.00001);
+    public void givenMovableAdapter_WhenConvertingMPHToKMPH_thenSuccessfullyConverted() {
+        Movable bugattiVeyron = new BugattiVeyron();
+        MovableAdapter bugattiVeyronAdapter = new MovableAdapterImpl(bugattiVeyron);
+        assertEquals(bugattiVeyronAdapter.getSpeed(), 431.30312, 0.00001);
+
+        Movable mcLaren = new McLaren();
+        MovableAdapter mcLarenAdapter = new MovableAdapterImpl(mcLaren);
+        assertEquals(mcLarenAdapter.getSpeed(), 387.85094, 0.00001);
+
+        Movable astonMartin = new AstonMartin();
+        MovableAdapter astonMartinAdapter = new MovableAdapterImpl(astonMartin);
+        assertEquals(astonMartinAdapter.getSpeed(), 354.0548, 0.00001);
     }
 }
 

core-java/src/test/java/com/baeldung/designpatterns/BridgePatternIntegrationTest.java

@@ -1,14 +1,7 @@
 package com.baeldung.designpatterns;
 
-import static com.baeldung.designpatterns.util.LogerUtil.LOG;
-import static org.hamcrest.CoreMatchers.is;
-import static org.junit.Assert.assertThat;
+import static org.junit.Assert.*;
 
-import java.util.List;
-
-import org.apache.log4j.spi.LoggingEvent;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 import com.baeldung.designpatterns.bridge.Blue;
@@ -18,35 +11,16 @@ import com.baeldung.designpatterns.bridge.Square;
 import com.baeldung.designpatterns.bridge.Triangle;
 
 public class BridgePatternIntegrationTest {
-    public static TestAppenderDP appender;
-    
-    @Before
-    public void setUp() {
-        appender = new TestAppenderDP();
-        LOG.addAppender(appender);
-    }
 	
     @Test
     public void whenBridgePatternInvoked_thenConfigSuccess() {
         //a square with red color
         Shape square = new Square(new Red());
-        square.drawShape();
+        assertEquals(square.draw(), "Square drawn. Color is Red");
         
         //a triangle with blue color
         Shape triangle = new Triangle(new Blue());
-        triangle.drawShape();
-
-        final List<LoggingEvent> log = appender.getLog();
-        
-        assertThat((String) log.get(0).getMessage(), is("Square drawn. "));
-        assertThat((String) log.get(1).getMessage(), is("Color : Red"));
-        assertThat((String) log.get(2).getMessage(), is("Triangle drawn. "));
-        assertThat((String) log.get(3).getMessage(), is("Color : Blue"));
-    }
-    
-    @After
-    public void tearDown() {
-        LOG.removeAppender(appender);
+        assertEquals(triangle.draw(), "Triangle drawn. Color is Blue");
     }
 }
 

core-java/src/test/java/com/baeldung/designpatterns/DecoratorPatternIntegrationTest.java

@@ -10,19 +10,16 @@ import com.baeldung.designpatterns.decorator.ChristmasTreeImpl;
 import com.baeldung.designpatterns.decorator.Garland;
 
 public class DecoratorPatternIntegrationTest {
-    private ChristmasTree tree;
-    
     @Test
     public void givenDecoratorPattern_WhenDecoratorsInjectedAtRuntime_thenConfigSuccess() {
-        //christmas tree with just one Garland
-        tree = new Garland(new ChristmasTreeImpl());
-        assertEquals(tree.decorate(), "Christmas tree with Garland");
+        ChristmasTree tree1 = new Garland(new ChristmasTreeImpl());
+        assertEquals(tree1.decorate(), 
+          "Christmas tree with Garland");
          
-        //christmas tree with two Garlands and one Bubble lights
-        tree = new BubbleLights(new Garland(
-          new Garland(new ChristmasTreeImpl()))
-        );
-        assertEquals(tree.decorate(), "Christmas tree with Garland with Garland with Bubble Lights");
+        ChristmasTree tree2 = new BubbleLights(
+          new Garland(new Garland(new ChristmasTreeImpl())));
+        assertEquals(tree2.decorate(), 
+          "Christmas tree with Garland with Garland with Bubble Lights");
     }
 }