Instance Variables
Definition
Instance variables are variables declared within a class but outside any method. They hold unique values for each instance (object) of the class and define the state or characteristics of an object.
Analogy
Think of instance variables as personal belongings that individuals have. Each person has their own set of belongings, such as clothes, gadgets, or books. Similarly, each object created from a class has its own set of instance variables that store specific values for that object.
Related terms
Methods: Methods are actions or behaviors associated with objects in a class. They define what an object can do or how it can interact with other objects.
Constructor: A constructor is a special method within a class that is automatically called when an object is created from that class. It initializes the object's state by assigning initial values to its instance variables.
Access Modifiers: Access modifiers determine the accessibility or visibility of classes, methods, and variables in object-oriented programming. They control which parts of a program can access certain elements and help enforce encapsulation and data hiding principles.
"Instance Variables" appears in:
Study guides (7)
AP Computer Science A - 2.1 Objects: Instances of Classes
AP Computer Science A - 5.1 Anatomy of a Class
AP Computer Science A - 5.2 Constructors
AP Computer Science A - 5.5 Mutator Methods
AP Computer Science A - 5.6 Writing Methods
AP Computer Science A - 5.7 Static Variables and Methods
AP Computer Science A - 9.3 Overriding Methods
Additional resources (2)
Practice Questions (4)
- What are the instance variables of the Student class?
- What is the difference between instance variables and local variables?
- Suppose we have a class named "Book" with instance variables "title" and "author." Which of the following constructor implementations correctly sets the instance variables?
- What can we do in the body of an enhanced for loop traversing an array of objects to change the objects' instance variables?
Resources
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