Merge pull request #6262 from soufiane-cheouati/master

Adding marker interfaces files

core-java-lang-oop/src/main/java/com/baeldung/markerinterface/DeletableShape.java

@@ -0,0 +1,5 @@
+package com.baeldung.markerinterface;
+
+public interface DeletableShape extends Shape {
+
+}

core-java-lang-oop/src/main/java/com/baeldung/markerinterface/Rectangle.java

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+package com.baeldung.markerinterface;
+
+public class Rectangle implements DeletableShape {
+
+    private double width;
+    private double height;
+
+    public Rectangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    @Override
+    public double getArea() {
+        return width * height;
+    }
+
+    @Override
+    public double getCircumference() {
+        return 2 * (width + height);
+    }
+}

core-java-lang-oop/src/main/java/com/baeldung/markerinterface/Shape.java

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+package com.baeldung.markerinterface;
+
+public interface Shape {
+    double getArea();
+    double getCircumference();
+}

core-java-lang-oop/src/main/java/com/baeldung/markerinterface/ShapeDao.java

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+package com.baeldung.markerinterface;
+
+public class ShapeDao {
+
+    public boolean delete(Object object) {
+        if (!(object instanceof DeletableShape)) {
+            return false;
+        }
+        // Calling the code that deletes the entity from the database
+
+        return true;
+    }
+
+}

core-java-lang-oop/src/test/java/com/baeldung/markerinterface/MarkerInterfaceUnitTest.java

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+package com.baeldung.markerinterface;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class MarkerInterfaceUnitTest {
+
+    @Test
+    public void givenDeletableObjectThenTrueReturned() {
+        ShapeDao shapeDao = new ShapeDao();
+        Object rectangle = new Rectangle(2, 3);
+
+        boolean result = shapeDao.delete(rectangle);
+        assertEquals(true, result);
+    }
+    
+    @Test
+    public void givenNonDeletableObjectThenFalseReturned() {
+        ShapeDao shapeDao = new ShapeDao();
+        Object object = new Object();
+
+        boolean result = shapeDao.delete(object);
+        assertEquals(false, result);
+    }
+}