1.10 Class Methods and Static Keyword

Static methods belong to the class

A static method (also called a class method) is marked with the `static` keyword and belongs to the class itself, not to any particular object. It can be called using the class name, like `Math.sqrt(25)`, without ever creating an instance of that class.

Static vs. instance methods

Instance methods operate on the data of a specific object and are called through an object reference. Static methods cannot access instance variables directly because there's no object involved — they only work with static (class) variables or their own parameters and local variables.

Common static examples

Utility classes like `Math` are full of static methods: `Math.pow()`, `Math.abs()`, `Math.random()`. Since these methods don't depend on object state, calling `new Math()` isn't needed — you simply write `Math.methodName(args)` directly using the class name.

Key terms

Static method

A method belonging to the class itself, marked with 'static', called using the class name without creating an object.

Instance method

A method that operates on a specific object's data; must be called through an object reference.

Why can't static methods use instance variables?

Because instance variables belong to individual objects, and static methods have no associated object.

Example of calling a static method

Math.sqrt(25) — called directly on the class name 'Math', no object needed.

Static variable

A variable shared by all instances of a class, accessible by static methods since it's not tied to any one object.

Try an AP-style question

How is a static method usually called?

1. With the class name, like Math.sqrt(9)
2. Only on a newly created object
3. Using the keyword this in front
4. It can't be called from anywhere