Java Chapter 8.4: Static Variables and Methods

Questions and Answers

What is a static variable?

Belongs to the class not to any object of the class.

What is a static method?

Not invoked on an object.

Provide an example of a static method.

Math.sqrt()

What is an example of defining a static method in a class?

public static double percentOf() Signup and view all the answers

Since static methods do not operate on an object, you cannot directly access any instance variables.

True Signup and view all the answers

What is another name for static variables?

Class variables. Signup and view all the answers

What are the uses of static variables?

Constants, passing data among objects, counters and accumulators for the entire class. Signup and view all the answers

Provide an example of a static variable using double as type and 'p' as the variable name.

static double p = 0; Signup and view all the answers

Can static methods reference instance variables?

False Signup and view all the answers

How can you define a static method?

Add the static modifier to the method definition. Signup and view all the answers

Static methods allow services that are not really associated with an object.

True Signup and view all the answers

How can a static method reference a variable?

They can only reference static variables or its own local variables. Signup and view all the answers

Study Notes

Static Variables

Static variables are tied to the class itself rather than individual instances of the class.
Also known as class variables, there is only one instance of the variable shared across all objects of the class.

Static Methods

Static methods are invoked on the class, not on objects, allowing access to class-level functionality.
To define a static method, add the static modifier to the method declaration.

Access and Limitations

Static methods cannot directly access instance variables because these variables are tied to specific objects, which do not exist when the static method is executed.
Static methods can reference static variables and local variables declared within their own scope.

Usage of Static Variables

Static variables are useful for:
- Defining constants.
- Sharing data among all instances of a class.
- Acting as counters or accumulators applicable to the entire class.

Examples

Example of a static method defining a financial calculation:

public class Financial {
    public static double percentOf() { /* method body */ }
}

Example of declaring static variables:

static double p = 0;
static double QUARTER = .25;

Key Concepts

Since static methods do not work on objects, they support functionalities that are not inherently tied to object states.
Example misuse in static methods, like calling x.sqrt() is incorrect; proper usage is Math.sqrt(x), highlighting the need for object consistency.

Description

Test your knowledge about static variables and methods in Java with this set of flashcards. Each card offers definitions and examples that clarify how static elements function within a class. Perfect for reinforcing key concepts in Java programming.