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Questions and Answers
What role does a class play in object-oriented programming?
What role does a class play in object-oriented programming?
Which principle in OOP allows programmers to create secure programs?
Which principle in OOP allows programmers to create secure programs?
How does inheritance contribute to the development of complex software projects?
How does inheritance contribute to the development of complex software projects?
What is the relationship between data and functions within a class?
What is the relationship between data and functions within a class?
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What is meant by data hiding in OOP?
What is meant by data hiding in OOP?
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What does data encapsulation in object-oriented programming primarily focus on?
What does data encapsulation in object-oriented programming primarily focus on?
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How do objects communicate in object-oriented programming?
How do objects communicate in object-oriented programming?
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In the context of OOP, what is a subclass?
In the context of OOP, what is a subclass?
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What is a defining characteristic of polymorphism in OOP?
What is a defining characteristic of polymorphism in OOP?
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Which of the following is NOT a characteristic of object-oriented programming?
Which of the following is NOT a characteristic of object-oriented programming?
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What does operator overloading allow in object-oriented programming?
What does operator overloading allow in object-oriented programming?
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Which of the following languages is commonly associated with object-oriented programming?
Which of the following languages is commonly associated with object-oriented programming?
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What happens when a derived class inherits from a base class?
What happens when a derived class inherits from a base class?
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What is a primary disadvantage of structured programming?
What is a primary disadvantage of structured programming?
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How are attributes defined in the context of an object?
How are attributes defined in the context of an object?
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What does the term 'object' refer to in object-oriented languages?
What does the term 'object' refer to in object-oriented languages?
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What is the main reason for hiding data within an object?
What is the main reason for hiding data within an object?
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What is the relationship between functions and data in structured programming?
What is the relationship between functions and data in structured programming?
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What characterizes behavior in the context of real-world objects?
What characterizes behavior in the context of real-world objects?
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Which statement best describes structured programming?
Which statement best describes structured programming?
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What happens when a change is made to a global data item in structured programming?
What happens when a change is made to a global data item in structured programming?
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Study Notes
Object-Oriented Programming (OOP) Overview
- OOP is a programming paradigm that combines data and functions into a single unit called an object.
- This contrasts with structured programming where data and functions are separate.
Books Mentioned
- Intro to Java Programming, Comprehensive Version, 10th Edition, by Y. Daniel Liang (2015), published by Prentice Hall.
- An Introduction to Object-Oriented Programming with Java, 5th Edition (2009).
Structured Programming
- A program in a procedural language is a list of instructions.
- A procedural program is divided into functions.
- Each function has a defined purpose and a defined interface to other functions.
- Dividing a program into functions is called structured programming.
Disadvantages of Structured Programming
- Large programs become overly complex.
- There's no data protection, allowing unrestricted access to global data by functions.
- Changing a single global data item may require modifying all functions that access it, making large programs difficult to modify.
- It's a poor model of the real world where functions and data aren't related.
- Real-world objects have both attributes and behaviors.
Object Attributes and Behavior
- Attributes (or characteristics) of real-world objects are equivalent to data in programs.
- Attributes are specific values like name, eye color, height, car color, horsepower, or number of doors.
- Behavior is what an object does in response to a stimulus like applying brakes in a car.
- Behavior is similar to a function to accomplish something.
Object-Oriented Languages
- The fundamental concept behind object-oriented languages is to combine data and functions that operate on that data into a single unit, called an object.
Objects
- An object consists of member data and a group of member functions.
- Objects' member functions provide the only way to access their member data.
- To read data, call a member function in the object; it accesses the data and returns the value.
- Direct access to object data isn't possible; data is hidden within the object.
OOP Characteristics
- Data and its functions are encapsulated into a single entity
- Data encapsulation and data hiding are key terms in Object-Oriented Programming (OOP).
- Modifying data involves calling an object's member function, which interacts only with that data.
- This simplifies the writing and modification of large and complex programs.
Object Communication
- Programs typically consist of numerous objects.
- Objects communicate with each other by calling each other's member functions.
- This communication is called sending messages.
Inheritance
- The vehicle class, for example, gets divided into cars, trucks, buses, motorcycles, etc.
- This division's principle is that each subcategory (subclass) shares features with the main category (class) from which it derives.
- Subcategories (e.g., types of vehicles) share common features (e.g., wheels, motor) from the parent category (vehicles).
- Each subclass also has unique characteristics. For instance, buses have many seats while trucks have hauling space.
- The original class is called the base class; derived classes share characteristics and further attributes.
Polymorphism
- OOP enables defining new behaviours for known operators (+, -, *). This is operator overloading.
- These operations are member functions of a specific class.
- Calling the overloaded operators essentially calls a specific member function within the class.
- Operator overloading is a type of polymorphism.
Popular Object-Oriented Programming Languages
- C++
- Java
- Smalltalk
- Eiffel
- Ruby
- Delphi
Characteristics of OOP
- Programs are divided into classes and functions.
- Data is hidden within an object and is not externally accessible.
- Inheritance facilitates the reuse of code.
- Adding new functions and data items is straightforward.
- Data holds more significance than functions.
- Data and functions are joined in a single unit called a class.
- Objects communicate by sending messages (in the form of functions).
Advantages of OOP
- Code reusability through inheritance.
- Complex projects divided into smaller functions.
- Abstraction and encapsulation lead to secure program development.
- Reduced software complexity.
- Data hiding enhances program safety.
- Enables rapid software development.
- Multiple instances of the same class can exist simultaneously without interference.
Introduction to Objects
- An object embodies something in a program with which interaction is possible.
- An object comprises member data and methods.
- Objects provide services that allow instructions for tasks to be performed.
- Classes define the services of objects.
- A class represents a concept, and an object is an instance of a class. Classes enable the creation of numerous objects.
Classes vs. Objects
- Classes represent conceptual models.
- Objects are real-world implementations embodying class characteristics.
- Multiple objects can be generated from a single class.
Class vs. Object
- A class is a blueprint or pattern for creating objects.
- Defining a class does not generate an object. This is comparable to creating a data type (int, float) - it doesn't automatically populate variables of these types.
- An object is an instance of a class (a specific example from the class' blueprint).
- A single class can be used to form numerous objects.
Classes (in Detail)
- Classes are new types of variables.
- Class definition specifies needed data and possible actions.
- Method is an object-oriented equivalent of a function.
Using Objects
- System.out object acts as output destination for instructions.
- Methods (e.g. println) are invoked on the object to execute actions.
Attributes of a Class
- Attributes, or variables, hold characteristics of a class' instances (objects).
- Attributes can be either variable or constant (constant preceded by "final").
- Each object shares the attribute definition but has a unique value for it.
- An object's attributes' current values are what determine its state.
Methods
- Methods represent actions or behaviors of class instances.
Methods of a Class
- Methods have specific formats for return types, access modifiers, and parameters.
Object Instantiation
- An object's instantiation creates or prepares a new object (a particular realization of a class blueprint).
- Instances of classes are objects.
- The format includes the class name, instance name, and instantiation keyword ('new').
Constructor
- A special method used to initialize an object's attributes upon creation/instantiation.
Default Constructor
- A constructor, if not defined, is automatically created and implicit within the Java language.
Calling Methods (Outside the Class)
- Calling a method requires prefacing the method with a class variable (which represents a reference to an object of that class)
Calling Methods (Inside the Class)
- Calling methods within a class directly refers to the method name.
Example (Code Snippet)
- Example code (showing object instantiation, class definition, method calls)
Private Keyword
-
privatekeyword syntactically specifies that class members aren't accessible outside the class. - The
privatekeyword is most often used for attributes (data members).
Encapsulation
- Encapsulation (information hiding) hides internal data; only defined methods may access private data members.
- Public methods can then access this private data via methods.
- This way, private data is protected from external modification.
- It also leads to preventing invalid states.
Assignment 1 (Problems)
- Write a program printing "Hello world"
- Write a program printing name, address, phone number.
- Create a rectangle class
- data members (length, height),
- methods to enter attributes, display them, compute area and perimeter and default constructor (initializing attributes to zero)
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Description
Explore the fundamentals of Object-Oriented Programming (OOP) as outlined in the 'Intro to Java Programming' and other key texts. Learn about the contrasts between OOP and structured programming, including the benefits and disadvantages of each paradigm. This quiz will assess your understanding of core concepts and terminology.
