Java_Polymorphism

Question 1

What is Polymorphism in Java? Give an example.

Answer 1

In the example below, we have created different types of Automobile using the InvetoryManager class taking a single class of Automobile which will refer to the similar type of objects. This is the idea of polymorphism.

• It means a class has the same interface or set of methods but different implementation.
• Polymorphism is the ability of anyone object(Automobile) to be referred by several different types of references.
• Polymorphism is about substitutability. This principle provides OOP languages like Java with extreme code flexibility.

Question 2

How does polymorphism look on a stack?

Answer 2

Always try “is a” rule for checking the parent-child inheritance for a valid polymorphism.

Question 3

Why use polymorphism?

Answer 3

Question 4

Benefits of polymorphism.

Answer 4

Question 5

What is object casting? Give an example.

Answer 5

Remember that casting just changes reference, it will not completely change the assignment.

// Here getSalary was defined in child, so cannot access child's methods
        Person p1 = new Employee("Keerhti", "Dadige", 19900101, 123, 20010101);
        System.out.println("Full Name: " + p1.getFullName());
        //System.out.println("Full Name: " + p1.getFullName() + " Salary: " + p1.getSalary());//p1 cannot access getSalary
        //To resolve above, we can do Object casting
        // Object Casting
        System.out.println("Full Name: " + p1.getFullName() + " Salary: " + ((Employee)p1).getSalary());

Question 6

How to protect the object casting at runtime?

Answer 6

Question 7

What is an Object class in Java?

Answer 7

Question 8

What happens when we append strings using + operator using String class?

Answer 8

Question 9

Override the equals() method of Object class using an example to compare two objects?

Answer 9