Exam 1z0-819 topic 1 question 29 discussion

If a class implements two interfaces, both of which have a default method with the same name and parameter types, then you must resolve the conflict. You should provide "conflict default" method in class and either implement your own greeting, or delegate to one of the conflicting methods, like this: Rectangle.super.caculateSurfaceArea(majorR, minorR);

If a class implements two interfaces, both of which have a default method with the same name and parameter types, then you must resolve the conflict. You should provide "conflict default" method in the class. There is a case with nearer definition/ For example public interface Point { default double calculateSurfaceArea(double, double) { ... } } public interface Rectangle extends Point { } public interface Ellipse extends Point { default double calculateSurfaceArea(double, double) { ... } } public class Cylinder implements Ellipse, Rectangle { } new Cylinder().calculateSurfaceArea(double, double) executes Ellipse method because of nearer definition.

The two interfaces have default methods, so if they didn't have the same name, Cylinder would not have to call any of them (because they already have a default implementation), so B is not correct. As the two methods in the two interfaces have the same name, the class that implements them must define its own implementation, so C is correct.

Tested in compiler. C is correct. It compiles when having only one method called calculatedSurfaceArea with two parameters in the child class.

C is correct. As a class implementing 2 interfaces with same(same signature) default method will cause a compile error.

B is correct

Duplicate default methods named calculatedSurfaceArea with the parameters (double, double) and (double, double) are inherited from the types Ellipse and Rectangle

C is correct because two same default methods create conflict for the compiler.

C is the correct answer

B is correct if a method implements two interfaces with same method signatures it has to provide an implementation to avoid conflict , same applies to abstract methods