A Brief Discussion of Static Methods

Overview

  1. Source Code Structure
  2. Implementing Point Class
  3. A Brief Discussion of Static Methods
  4. Implementing Rectangle Class
  5. Testing
  6. Constructor to Make a Rectangle Copy
  7. Extra Credit: Class Invariant

So, up until now every time we have invoked a method, we have invoked it ON an object. That is, we make an object, 
Fraction f = new Fraction(3, 4);
and then we do something with that object: 
f.decimalValue();

But in the last step, we simply made a call to Math.pow() without making an object first. 

double d = Math.pow(3, 2);

The reason that works is the methods in Math are declared as static. Static means you can make function calls WITHOUT an actual object. So it makes sense that a method that squares something doesn't need to operate on a particular object, whereas a method like decimalValue() must be called on a SPECIFIC fraction.

Note that because static methods do not refer to an object, they can't access any instance variables except those that are declared as static.

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