Java Polymorphism: Exercises, Practice, Solution
Java Polymorphism Exercises [6 exercises with solution]
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In Core, Java Polymorphism is one of easy concept to understand. Polymorphism definition is that Poly means many and morphos means forms. It describes the feature of languages that allows the same word or symbol to be interpreted correctly in different situations based on the context. There are two types of Polymorphism available in Java. For example, in English, the verb “run” means different things if you use it with “a footrace,” a “business,” or “a computer.” You understand the meaning of “run” based on the other words used with it. Check out this article for more information.
1. Write a Java program to create a base class Animal (Animal Family) with a method called Sound(). Create two subclasses Bird and Cat. Override the Sound() method in each subclass to make a specific sound for each animal.
2. Write a Java program to create a class Vehicle with a method called speedUp(). Create two subclasses Car and Bicycle. Override the speedUp() method in each subclass to increase the vehicle's speed differently.
3. Write a Java program to create a base class Shape with a method called calculateArea(). Create three subclasses: Circle, Rectangle, and Triangle. Override the calculateArea() method in each subclass to calculate and return the shape's area.
4. Write a Java program to create a class Employee with a method called calculateSalary(). Create two subclasses Manager and Programmer. In each subclass, override the calculateSalary() method to calculate and return the salary based on their specific roles.
5. Write a Java program to create a base class Sports with a method called play(). Create three subclasses: Football, Basketball, and Rugby. Override the play() method in each subclass to play a specific statement for each sport.
6. Write a Java program to create a class Shape with methods getArea() and getPerimeter(). Create three subclasses: Circle, Rectangle, and Triangle. Override the getArea() and getPerimeter() methods in each subclass to calculate and return the area and perimeter of the respective shapes.
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Java: Tips of the Day
Hashset vs Treeset:
HashSet is much faster than TreeSet (constant-time versus log-time for most operations like add, remove and contains) but offers no ordering guarantees like TreeSet.
- the class offers constant time performance for the basic operations (add, remove, contains and size).
- it does not guarantee that the order of elements will remain constant over time
- iteration performance depends on the initial capacity and the load factor of the HashSet.
- It's quite safe to accept default load factor but you may want to specify an initial capacity that's about twice the size to which you expect the set to grow.
- guarantees log(n) time cost for the basic operations (add, remove and contains)
- guarantees that elements of set will be sorted (ascending, natural, or the one specified by you via its constructor) (implements SortedSet)
- doesn't offer any tuning parameters for iteration performance
- offers a few handy methods to deal with the ordered set like first(), last(), headSet(), and tailSet() etc
- Both guarantee duplicate-free collection of elements
- It is generally faster to add elements to the HashSet and then convert the collection to a TreeSet for a duplicate-free sorted traversal.
- None of these implementations are synchronized. That is if multiple threads access a set concurrently, and at least one of the threads modifies the set, it must be synchronized externally.
- LinkedHashSet is in some sense intermediate between HashSet and TreeSet. Implemented as a hash table with a linked list running through it, however,it provides insertion-ordered iteration which is not same as sorted traversal guaranteed by TreeSet.
So a choice of usage depends entirely on your needs but I feel that even if you need an ordered collection then you should still prefer HashSet to create the Set and then convert it into TreeSet.
- e.g. SortedSet<String> s = new TreeSet<String>(hashSet);
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