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Questions and Answers
What aspect of an object in object-oriented programming defines what the object can do?
What aspect of an object in object-oriented programming defines what the object can do?
- State
- Properties
- Methods (correct)
- Identity
Which of the following statements about constructors is true?
Which of the following statements about constructors is true?
- The name of a constructor must differ from the class name. (correct)
- Constructors are invoked using the delete operator.
- Constructors cannot accept parameters.
- Constructors can have a return type.
What is a no-arg constructor?
What is a no-arg constructor?
- A constructor that has no parameters. (correct)
- A constructor that cannot be invoked.
- A constructor that initializes multiple objects.
- A constructor that takes one parameter.
Which line of code correctly creates a new object of the Circle class?
Which line of code correctly creates a new object of the Circle class?
What is implicitly defined in a class if no constructors are explicitly declared?
What is implicitly defined in a class if no constructors are explicitly declared?
How is an object's state characterized in object-oriented programming?
How is an object's state characterized in object-oriented programming?
What does the reference variable do in object-oriented programming?
What does the reference variable do in object-oriented programming?
Which statement accurately describes the identity of an object?
Which statement accurately describes the identity of an object?
What is the purpose of a constructor in a class?
What is the purpose of a constructor in a class?
Which of the following is NOT a characteristic of an object?
Which of the following is NOT a characteristic of an object?
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Study Notes
Object-Oriented Programming (OOP) Concepts
- OOP involves programming with objects, representing real-world entities.
- Examples of objects include a student, desk, circle, button, or loan.
- An object has three core features: unique identity, state, and behaviors.
- The state consists of data fields (properties) holding current values.
- The behavior of an object is demonstrated through methods.
Understanding Classes
- Classes define a blueprint for creating objects of the same type.
- In Java, classes employ variables for data fields and methods for behaviors.
- Classes include constructors, special methods for creating and initializing objects.
Constructors and Their Role
- A no-arg constructor is a constructor without parameters.
- Constructors share the name with their class and do not have a return type.
- They are invoked using the new operator to create objects.
- Example of object instantiation:
new Circle();ornew Circle(5.0);
Default Constructors
- If no constructors are defined, a default constructor is automatically provided.
- The default constructor is a no-arg constructor with an empty body.
Declaring Object Reference Variables
- Object reference variables enable access to objects in Java.
- Declaration syntax:
ClassName objectRefVar; - Example:
Circle myCircle;
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