BAEL-1072 - Difference between Proxy, Decorator, Adapter, and Bridge Patterns (#2390)

* Structural Design Patterns 

Difference between several types of structural design patterns

* Structural Design Pattern

Difference between several types of structural design patterns

* Structural Design Patterns

Difference between several types of structural design patterns

* Structural Design Patterns

Difference between several types of structural design patterns

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

@@ -0,0 +1,20 @@
+package com.baeldung.designpatterns;
+
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+import com.baeldung.designpatterns.adapter.LuxuryCarsSpeedAdapter;
+import com.baeldung.designpatterns.adapter.LuxuryCarsSpeedAdapterImpl;
+
+public class AdapterPatternIntegrationTest {
+    @Test
+    public void givenLuxuryCarsAdapter_WhenConvertingMPHToKMPH_thenSuccessfullyConverted() {
+        LuxuryCarsSpeedAdapter luxuryCars = new LuxuryCarsSpeedAdapterImpl();
+        assertEquals(luxuryCars.bugattiVeyronInKMPH(), 431.30312, 0.00001);
+        assertEquals(luxuryCars.mcLarenInKMPH(), 387.85094, 0.00001);
+        assertEquals(luxuryCars.astonMartinInKMPH(), 354.0548, 0.00001);
+    }
+}
+

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

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+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 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;
+import com.baeldung.designpatterns.bridge.Red;
+import com.baeldung.designpatterns.bridge.Shape;
+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();
+        
+        //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);
+    }
+}
+

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

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+package com.baeldung.designpatterns;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.baeldung.designpatterns.decorator.BubbleLights;
+import com.baeldung.designpatterns.decorator.ChristmasTree;
+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");
+        
+        //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");
+    }
+}
+

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

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+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 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.proxy.ExpensiveObject;
+import com.baeldung.designpatterns.proxy.ExpensiveObjectProxy;
+
+public class ProxyPatternIntegrationTest {
+    public static TestAppenderDP appender;
+    
+    @Before
+    public void setUp() {
+        appender = new TestAppenderDP();
+        LOG.addAppender(appender);
+    }
+    
+    @Test
+    public void givenExpensiveObjectProxy_WhenObjectInitialized_thenInitializedOnlyOnce() {
+        ExpensiveObject object = new ExpensiveObjectProxy();
+        object.process();
+        object.process();
+
+        final List<LoggingEvent> log = appender.getLog();
+        
+        assertThat((String) log.get(0).getMessage(), is("Loading initial configuration..."));
+        assertThat((String) log.get(1).getMessage(), is("processing complete."));
+        assertThat((String) log.get(2).getMessage(), is("processing complete."));
+    }
+    
+    @After
+    public void tearDown() {
+        LOG.removeAppender(appender);
+    }
+}
+

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

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+package com.baeldung.designpatterns;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.log4j.AppenderSkeleton;
+import org.apache.log4j.spi.LoggingEvent;
+
+public class TestAppenderDP extends AppenderSkeleton {
+    private final List<LoggingEvent> log = new ArrayList<LoggingEvent>();
+
+    @Override
+    public boolean requiresLayout() {
+        return false;
+    }
+
+    @Override
+    protected void append(final LoggingEvent loggingEvent) {
+        log.add(loggingEvent);
+    }
+
+    @Override
+    public void close() {
+    }
+
+    public List<LoggingEvent> getLog() {
+        return new ArrayList<LoggingEvent>(log);
+    }
+}