Introduction
That post was based on Vogella's post about an introduction of Java.
Multiple Inheritance of Methods.
Java follows an especific priority order to decide which method should be used among the classes (Super Classes or Interfaces) that have their implementations.
- Overrides methods.
- Super Class methods.
- Subtype methods (instead of Supertypes one).
For example, let's consider the following Interfaces and Super Class:
interface MyFirstInterface { // Supertype
public default void myMethod(String myParameter) {
System.out.println("First Message: " + myParameter);
}
}
interface MySecondInterface extends MyFirstInterface { // Subtype
public default void myMethod(String myParameter) {
System.out.println("Second Message: " + myParameter);
}
}
class MySuperClass {
public void myMethod(String myParameter) { // Super class
System.out.println("Super Class Message: " + myParameter);
}
}
Using MySuperClass as Super Class, implemmenting both Interfaces and overriding the myMethod method in a test class, according to the priority order, it is expected that the overrided method will be executed.
Code:
class Application extends MySuperClass implements MyFirstInterface, MySecondInterface {
public static void main(String args[]) {
Application myApp = new Application();
myApp.myMethod("Hello World!");
}
@Override
public void myMethod(String myParameter) {
System.out.println("Overrided Message: " + myParameter);
}
}
Result:
Overrided Message: Hello World!
Using MySuperClass as Super Class and implemmenting both Interfaces at the same test class, according to the priority order, it is expected that the Super Class's method will be executed.
Code:
class Application extends MySuperClass implements MyFirstInterface, MySecondInterface {
public static void main(String args[]) {
Application myApp = new Application();
myApp.myMethod("Hello World!");
}
}
Result:
Super Class Message: Hello World!
Implemmenting only both Interfaces at the test class, according to the priority order, it is expected that the Subtype's method (MySecondInterface.myMethod) will be executed.
Code:
class Application implements MyFirstInterface, MySecondInterface {
public static void main(String args[]) {
Application myApp = new Application();
myApp.myMethod("Hello World!");
}
}
Result:
Second Message: Hello World!
As shown above, this is the list of priorities that Java assumes when encountering these scenarios. You can see the code by clicking here.
Any suggestions are accepted, thank you for reading ;D.
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