It is often the case that two or more classes share a common set of methods. For

Question

It is often the case that two or more classes share a common set of methods. For programming purposes we might wish to treat the objects of those classes in a similar way by invoking some of their common routines. For example, the Dog and cat classes listed below agree on the void method speak. Because Dog and cat objects have the ability to "speak, " it is natural to think of putting both types of objects in an ArrayList and invoking speak on every object in the list. Is this possible? Certainly we could create an ArrayList of Dog that would hold all the Dog objects, but can we then add a cat object to an ArrayList of Dog? Try running the main program below as it is written. Run it a second time after uncommenting the line that instantiates a cat object and tries to add it to the ArrayList.

Explanation / Answer

Q5)

All methods of Interface in Java are PUBLIC.

So when we override any methods, then we can not narrower the visibilityu of that
methods in subclass

So, inventory is implementing Measurable interface

getMeasure is public as it is defined in Measurable interface
So, when a class implementing Measurable and try to implementing getMeasure method,
it visibility should be public

Q6)

No, We can not add a Cat Object in the arraylist of of type Dog object.

We will be able to put Cat object in ArrayList of type Dog if Cat is child class of Dog.

TO Solve the above problem, we should create a Animal class and put all common methods in Animal class and make Dog class and Cat class to extends Animal class. THen create a ArrayList of type Animal and then we can put Dog as well as Cat Obejct in ArrayList

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