Added adapter pattern and its test case

Author: abhijay94

src/main/java/com/designpatterns/structural/adapter/BugattiVeyron.java

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+package src.main.java.com.designpatterns.structural.adapter;
+
+public class BugattiVeyron implements Movable {
+    @Override
+    public double getSpeed() {
+        return 268;
+    }
+}

src/main/java/com/designpatterns/structural/adapter/Movable.java

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+package src.main.java.com.designpatterns.structural.adapter;
+
+public interface Movable {
+    // Returns the speed of the movable in MPH
+    double getSpeed();
+}

src/main/java/com/designpatterns/structural/adapter/MovableAdapter.java

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+package src.main.java.com.designpatterns.structural.adapter;
+
+/**
+ * An Adapter pattern acts as a connector between two incompatible interfaces that otherwise cannot be connected
+ * directly. An Adapter wraps an existing class with a new interface so that it becomes compatible with the client’s
+ * interface.
+ * <br>
+ * The main motive behind using this pattern is to convert an existing interface into another interface that the client
+ * expects. It’s usually implemented once the application is designed.
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Adapter_pattern">Adapter Pattern</a>
+ */
+public interface MovableAdapter {
+    // Returns the speed of the movable in KPH
+    double getSpeed();
+}

src/main/java/com/designpatterns/structural/adapter/MovableAdapterImpl.java

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+package src.main.java.com.designpatterns.structural.adapter;
+
+public class MovableAdapterImpl implements MovableAdapter {
+    private Movable luxuryCars;
+
+    public MovableAdapterImpl(Movable luxuryCars) {
+        this.luxuryCars = luxuryCars;
+    }
+
+    @Override
+    public double getSpeed() {
+        return convertMPHtoKMPH(luxuryCars.getSpeed());
+    }
+
+    private double convertMPHtoKMPH(double mph) {
+        return mph * 1.60934;
+    }
+}

src/test/java/com/designpatterns/structural/MovableAdapterTest.java

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+package src.test.java.com.designpatterns.structural;
+
+import org.junit.Test;
+import src.main.java.com.designpatterns.structural.adapter.BugattiVeyron;
+import src.main.java.com.designpatterns.structural.adapter.Movable;
+import src.main.java.com.designpatterns.structural.adapter.MovableAdapter;
+import src.main.java.com.designpatterns.structural.adapter.MovableAdapterImpl;
+
+import static org.junit.Assert.assertEquals;
+
+public class MovableAdapterTest {
+    @Test
+    public void testMovableAdapter() {
+        Movable bugattiVeyron = new BugattiVeyron();
+        MovableAdapter bugattiVeyronAdapter = new MovableAdapterImpl(bugattiVeyron);
+        assertEquals(bugattiVeyronAdapter.getSpeed(), 431.30312, 0.00001);
+    }
+}