Object Oriented Programming Using Java – Unit III Q&A
1. What is an interface?
An interface in Java is a collection of abstract methods and static constants. It is used to achieve full abstraction and multiple inheritance.
2. Define method overriding.
Method overriding occurs when a subclass provides a specific implementation of a method already defined in its superclass. The method must have the same name, return type, and parameters.
3. What is dynamic method dispatch?
Dynamic method dispatch is a mechanism where method calls are resolved at runtime instead of compile-time. It supports runtime polymorphism.
4. What is the purpose of super keyword?
The super keyword refers to the immediate parent class object and removes confusion between superclass and subclass members.
5. Mention any two uses of super.
1. To call the parent class constructor.
2. To access parent class variables or methods.
6. What is an abstract class?
An abstract class is declared using the abstract keyword and cannot be instantiated. It may contain both abstract and concrete methods.
8. What is the use of final keyword?
The final keyword restricts modification. It can make variables constant, prevent method overriding, and stop inheritance.
10. What is a package in Java?
A package is a collection of related classes and interfaces used to organize code and avoid naming conflicts.
12. What is an exception?
An exception is an unexpected event that occurs at runtime and disrupts normal program flow.
13. What is the purpose of try–catch block?
The try block contains risky code, while the catch block handles exceptions to prevent program crashes.
15. What is the difference between throw and throws?
throw is used to explicitly throw an exception.
throws is used in a method signature to declare exceptions.
16. What is a user-defined exception?
A user-defined exception is created by extending java.lang.Exception to handle custom application errors.