WLU Zara hamid CP213 Object-Oriented Programming Final Exam Notes 2025 COMPLETE UPDATE Wilfrid Laurier University

WLU Zara hamid CP213 Object-Oriented
Programming Final Exam Notes 2025 COMPLETE
UPDATE Wilfrid Laurier University




Interfaces:
- Definition: An interface in Java is a blueprint of a class. It contains abstract methods that
define the behavior a class must implement.
- Syntax: Defined using the interface keyword followed by the interface name and method
signatures.
- Abstract Methods: Interfaces contain method signatures without implementations.
Classes implementing an interface must provide concrete implementations for all
interface methods.
- Multiple Interfaces: A class can implement multiple interfaces, allowing it to inherit and
define behaviour from multiple sources.
- Implementation: To implement an interface, a class uses the implements keyword
followed by the interface name and implements all the methods declared in that
interface.

Multiple Inheritances:
- Inheriting from Multiple Classes: Java doesn't support multiple class inheritance (where
a class directly extends more than one class), as it can lead to ambiguity and
complexities in the inheritance hierarchy.
- Interface Multiple Inheritance: Java supports multiple inheritance through interfaces. A
class can implement multiple interfaces, inheriting their abstract methods.
- Resolution of Multiple Inheritance: When a class implements multiple interfaces with
conflicting method signatures, it must provide concrete implementations for all conflicting
methods. This resolves ambiguity.
Inner and Outer Classes:
- Outer Classes:
- Definition: An outer class is a regular class in Java. It stands independently and
can exist without any association with other classes.
- Syntax: An outer class is defined in the typical manner, outside of any other class
or method.
- Visibility: The members (fields, methods) of an outer class can have different
access modifiers (public, private, protected, default) controlling their accessibility
from other classes.

,- Inner Classes:
- Definition: An inner class is a class defined within another class.
- Syntax: Inner classes are defined within the body of another class.
- Types of Inner Classes:
- Member Inner Class: Non-static inner class defined at the member level of
another class. It has access to all members (including private) of the outer class.
- Static Nested Class: Inner class defined as static within another class. It doesn’t
have access to the instance variables/methods of the outer class without an
object.
- Local Inner Class: Defined inside a block of code, typically within a method. Only
accessible within that method.

, - Anonymous Inner Class: A special case of a local inner class without a name,
often used for event handling or defining behavior in-line.
- Characteristics and Usage:
1. Accessing Members:
- Inner classes can access private members of the outer class directly.
- Outer classes cannot directly access members of inner classes.
2. Relationship:
- Inner classes are tightly bound to the outer class. An instance of the inner class
must be created within an instance of the outer class.
- An inner class instance has access to the outer class instance that created it.
3. Scope:
- Inner classes can access any members of the outer class, even if they are
private.
- Outer classes cannot directly access members of inner classes.
4. Instance Creation:
- To create an instance of the inner class, it must be associated with an instance of
the outer class.
- Syntax: OuterClass.InnerClass innerObject = outerObject.new InnerClass();
5. Use Cases:
- Inner classes are used to logically group classes that are only used in one place.
- They are especially useful in event handling and GUI programming, providing a
way to implement listeners and handlers.
6. Encapsulation and Readability:
- Inner classes can increase encapsulation and improve code readability by
logically grouping classes and interfaces in one place.
7. Privacy and Access Control:
- Inner classes can access private members of the outer class, enabling
encapsulation without exposing implementation details.




Exception Handeling:
- Basics:
- What are Exceptions? Exceptions are unexpected events that occur during the
execution of a program, disrupting the normal flow of the code.
- Purpose of Exception Handling: Exception handling allows developers to manage
and recover from these unexpected events, preventing abrupt termination of the
program.
- Keywords and Constructs:
- try, catch, finally:
- try block: Contains the code where an exception might occur.
- catch block: Catches and handles exceptions thrown within the try block.
- finally block: Executes code regardless of whether an exception occurred
or not. Typically used for cleanup tasks.