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

@@ -1,7 +1,5 @@
 package com.baeldung.markerinterface;
 
-public interface DeletableShape {
-    double getArea();
+public interface DeletableShape extends Shape {
 
-    double getCircumference();
-}
+}

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

@@ -1,6 +1,6 @@
 package com.baeldung.markerinterface;
 
-public class Rectangle implements Deletable {
+public class Rectangle implements DeletableShape {
 
     private double width;
     private double height;

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

@@ -0,0 +1,6 @@
+package com.baeldung.markerinterface;
+
+public interface Shape {
+    double getArea();
+    double getCircumference();
+}

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

@@ -3,7 +3,7 @@ package com.baeldung.markerinterface;
 public class ShapeDao {
 
     public boolean delete(Object object) {
-        if (!(object instanceof Deletable)) {
+        if (!(object instanceof DeletableShape)) {
             return false;
         }
         // Calling the code that deletes the entity from the database