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What is a broad definition of class and what does it do?
What is a broad definition of class and what does it do?
An abstract description of objects that defines an object as having data and behaviors. This class acts as a template for objects used in another class.
A class may describe...
A class may describe...
What is a hollow class or main class?
What is a hollow class or main class?
Classes which are just simple programs, rather than object-oriented programs.
What is data in terms of classes?
What is data in terms of classes?
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What are behaviors in terms of classes?
What are behaviors in terms of classes?
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What is an object?
What is an object?
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What is a constructor?
What is a constructor?
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What will happen if you don't write a constructor?
What will happen if you don't write a constructor?
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How do you reference an object's data?
How do you reference an object's data?
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How do you reference an object's method?
How do you reference an object's method?
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What is a key attribute of an instance variable and an instance method?
What is a key attribute of an instance variable and an instance method?
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What is a key attribute of a class variable, constant, and method?
What is a key attribute of a class variable, constant, and method?
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If a class is like a cookie cutter, an object is like what?
If a class is like a cookie cutter, an object is like what?
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Where do objects come from?
Where do objects come from?
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Where does the first object come from?
Where does the first object come from?
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What does the static keyword mean?
What does the static keyword mean?
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What is an anonymous object?
What is an anonymous object?
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When will a class be given a default constructor?
When will a class be given a default constructor?
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Which operator is used to access a data field or invoke a method from an object?
Which operator is used to access a data field or invoke a method from an object?
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What is object-oriented programming?
What is object-oriented programming?
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What properties must a constructor's name have?
What properties must a constructor's name have?
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What is a constructor method responsible for?
What is a constructor method responsible for?
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Can a constructor method take arguments?
Can a constructor method take arguments?
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What are some rules constructor methods must follow?
What are some rules constructor methods must follow?
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What does the 'this' keyword do?
What does the 'this' keyword do?
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What can the default constructor do?
What can the default constructor do?
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Why should you always have a default constructor?
Why should you always have a default constructor?
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When do you make a blank default constructor?
When do you make a blank default constructor?
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What are the 3 main rules of method overloading?
What are the 3 main rules of method overloading?
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How do you use UML notation?
How do you use UML notation?
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Study Notes
Classes and Objects Overview
- A class serves as an abstract blueprint for creating objects, defining their data attributes and methods (behaviors).
- A class can represent various instances, from a single object to multiple related objects.
- Hollow classes contain simple programs without object-oriented features.
Key Components of Classes
- Attributes (or properties) refer to the data associated with a class, defining its state.
- Methods represent the behaviors or functions that class objects can perform.
Objects and Instances
- An object is an instance of a class, encapsulating both data and behaviors as defined by the class.
- Objects are created through a piece of code called a constructor, which initializes the object's state.
Constructors
- If a constructor is not explicitly defined, Java automatically generates a default constructor.
- Constructors must have the same name as the class and cannot have a return type, not even void.
Object References
- The dot operator (.) is used to access an object's data fields and to invoke its methods.
- Data fields are referenced with the format:
objectReference.data
, and methods withobjectReference.method()
.
Instance vs Class Attributes
- Instance variables are specific to individual object instances, while instance methods are invoked by each instance.
- Class variables are shared across all instances, and class methods are not tied to any specific instance.
Program Structure
- The main method initializes program execution but is not tied to any object; it belongs to the class itself.
- Anonymous objects are instantiated without being assigned to a reference variable.
Default Constructors
- A class is given a default constructor when no constructors are explicitly defined.
- It can be blank when no initializations are required, but it's important for flexibility in object creation.
Method Overloading
- Method overloading requires methods to have the same name but different parameter lists or return types.
- The same name can be reused, enabling multiple methods to coexist with distinct functionalities.
Additional Concepts
- The
this
keyword differentiates instance variables from local variables with the same name. - Understanding UML notation can aid in visualizing class structures and relationships.
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Test your knowledge on the fundamental concepts of classes and objects in programming. These flashcards cover definitions, examples, and key characteristics that differentiate classes from simple programs. Perfect for anyone looking to strengthen their understanding of object-oriented programming.