Adding marker interfaces files

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

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

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

@@ -0,0 +1,7 @@
+package com.baeldung.markerinterface;
+
+public interface DeletableShape {
+    double getArea();
+
+    double getCircumference();
+}

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

@@ -0,0 +1,22 @@
+package com.baeldung.markerinterface;
+
+public class Rectangle implements Deletable {
+
+    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/ShapeDao.java

@@ -0,0 +1,14 @@
+package com.baeldung.markerinterface;
+
+public class ShapeDao {
+
+    public boolean delete(Object object) {
+        if (!(object instanceof Deletable)) {
+            return false;
+        }
+        // Calling the code that deletes the entity from the database
+
+        return true;
+    }
+
+}