gistfile1.txt

public class TestClass {

    public void methoda() {
        List<ClassB> aList = new ArrayList<ClassB>();

        ClassB b = new ClassB();

        aList.add(b);
        
        List<TestInterface> bList = new ArrayList<TestInterface>();
        bList.add(b);
        
        
        TestInterface zz = aList.get(0);
        
        TestInterface zz2 = bList.get(0);
        
    }
}

class ClassB implements TestInterface {
    public void methodA() {
        return;
    }
}

interface TestInterface {
    void methodA();
}