Inheritance versus composition in Java
This article illustrates the concepts of inheritance and composition in Java. The first example will help you understand inheritance. The later examples will help you understand how to use composition to improve your use of inheritance.
Multiple inheritance in Java. Comparison of composition and inheritance
This article examines multiple inheritance and then explores the benefits of composition over inheritance.
3
Task
Java Core, level 3, lesson 2
Beer
There's no such thing as too much programming... But "too much beer" can result in "it's time to go home" or "sleep on the floor". In this task, you will get two interfaces. The BeerLover class needs to implement one of them. At the same time, you need to understand the relationship between the READY_TO_GO_HOME variable and the isReadyToGoHome method.
3
Task
Java Core, level 3, lesson 2
Beer. Part 2. The recovery.
Beer can be both alcoholic and nonalcoholic. The difference is huge. But no matter what type of beer you have, it is the process of drinking that unites man with beer. In this task, we will only drink alcoholic beer. Enable the Drink interface in the AlcoholicBeer class and implement all of its methods.
3
Task
Java Core, level 3, lesson 2
Don't mix beer with cola
Do you prefer beer or cola? Perhaps it depends on your mood? Either way, the most logical interface between humans and beer or between humans and cola can be expressed in a single word: "drink". Implement the Drink interface in the Beer and Cola classes.
3
Task
Java Core, level 3, lesson 2
Selectable and Updatable
Galaxy Rush's engineering department decided to set up a surveillance system for Planet Wild Robots. Your task is simple: make a Screen class that implements the Selectable and Updatable interfaces.
8
Task
Java Core, level 3, lesson 2
Four mistakes
Once again you're working on someone else's code, and once again you have to fix their mistakes. You'll need to gradually get used to this process. Luckily, this time, it's a very simple task about interfaces, with only 33 lines of code. So, no whining, just get going and fix the bugs. Hint: There are only four bugs.
8
Task
Java Core, level 3, lesson 2
Buggy initializeIdAndName
Something's wrong with this code! Your task is to fix the program so that it compiles and runs. First, figure out why it isn't working and then implement the initializeIdAndName method in the User class. In this case, the User class's initializeIdAndName method must return a User.
3
Task
Java Core, level 3, lesson 2
Parameterized interface
Remember generics? They are generalizations - parametrized types, right? If not, rack your brain, then search through the lessons, and then search Google. Or use a different order if you'd like. Then, look at this task's code and make the StringObject class implement the SimpleObject interface using a String parameter.
3
Task
Java Core, level 3, lesson 2
Hey, are you alive?
The program you are going to write should answer this question. To accomplish this, create a Person interface and add an isAlive() method, which will return whether the Person object is alive. Can you guess which type this method should return?
3
Task
Java Core, level 3, lesson 2
All that moves
We are going to create an interface for anything that can move. We'll call it CanMove and give it a speed method. And CanMove will be inherited by all things that moveth upon the ground, and that which moveth through the air. And each shall have its own speed method. And then thou shalt behold it and see a job well done!
3
Task
Java Core, level 3, lesson 2
Who's that smarty?
Do you know the difference between Smart and Clever? We do too, but that's a topic for another day. Today we're talking about adding the Secretary and Boss interfaces to the Manager and Subordinate classes. Try to figure out for yourself which interface is best for each class. Good luck!