Abstract class or interface: JAVA?

Question

I have one common method that I need to use in several classes with only one call to the calling class. So, what I see, I can call it two ways.

public abstract class TestAbstractClass {
    void commonMethod(){
        System.out.println("Calling common method : TestAbstractClass");
    }
}

calling class:

public class RunApplication extends TestAbstractClass{

    public void testMethod(){
        commonMethod();
    }
}

[OR]

Uses the default Java 8 feature in the interface.

public interface TestInterface {
    default void commonMethod(){
        System.out.println("Calling common method : TestInterface");
    }
}

calling class:

public class RunApplication implements TestInterface{

    public void testMethod(){
        commonMethod();
    }
}

They both work great for me, but what works best is an abstract class with a non-abstract method OR An interface with a standard method.

Answer 1

Abstract class or interface

If I were you, I will judge the appropriateness by checking whether all these classes are related or not.

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Answer 2

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Answer 3

Inheritance in any form is intended for use with polymorphism.

If you have a general method, don't just push it to a superclass, but consider using a separate class to wrap it. Thus, you can later use the refactoring code to use the strategy design pattern in case of any fluctuations in the general method.