Use methods declared in implementation that are not defined in interface

Question

I have a class defined by an interface

public interface Test {
    void testMethod();
}

Test test = new TestImpl();

public class TestImpl implements Test {         


        

Answer 1

If you want to avoid casting directly to your implementation class, I would create another interface:

public interface SpecificTest extends Test { 
    void anotherMethod();
}

And then have your TestImpl implement that interface (which means you can declare it as either Test or SpecificTest ):

SpecificTest test = new TestImpl();
test.anotherMethod();