Writing your own Static Methods

Learn to write static methods, which play a similar role to ordinary functions in other languages.

We'll cover the following

The main unit of organization in a Java program is the class. The simplest Java program contains just one class. Among other things, a class is a collection of methods.

There are two types of methods: static methods and non-static methods. We will focus on static methods first, since they are simpler. A static method plays a similar role to an ordinary function in other languages.

In any language, factoring is the process of reorganizing code into different functions/methods, classes, files, or libraries.

You will factor some code into new static methods in the following exercise.

Exercise: factor smiley

The code below has a single static method, called main. The method is declared using the keywords public static void, the name of the function, parentheses containing parameters for the function (String[] args), an open curly brace ({), and a closing curly brace (}).

You have to do the following:

  1. Write three static methods: drawOutline, drawMouth, and drawEyes. These methods should take no parameters, and you can use the keywords public static void to define them. If you usually code in Python, don’t forget the curly braces.

  2. Factor the drawing code, except c.draw(), into these functions. Leave the code c = new Canvas(200, 200); in main. The variable c will be available to all three of these functions, since it is declared in the class, outside of any function. This is necessary so that you can make calls to c.circle, etc.

  3. Call your functions from main using drawOutline(), etc., to draw the smiley. (static methods within the same class can be called just like functions in other languages, so no dot (.) is required.)

import com.educative.graphics.*;
class SmileyFactored {
  static Canvas c;
  public static void main(String[] args) {
    
    c = new Canvas(200, 200);
    
    // Draw the outline of the face
    c.fill("yellow");
    c.stroke("black");
    c.circle(100, 100, 50);
    
    // draw the mouth
    c.stroke("black");
    c.fill("yellow");
    c.circle(100, 100, 30);
    c.stroke("yellow");
    c.rect(68, 68, 62, 40);
   
    // draw the eyes
    c.stroke("black");
    c.fill("black");
    c.circle(100 - 20, 100 - 10, 5);
    c.circle(100 + 20, 100 - 10, 5);
   
    c.draw();
  }
}

Check your work

There is a sample solution in the tab labelled SmileyFactoredSolution.java above. Compare it to your solution. Here are a few things to look for in terms of coding style:

  1. Comments: Do each of your methods have a comment at the top that describes the intent of the method?

  2. Indentation: Every method declaration in a class should be indented one level. Then, the body of the method should be indented another level as well.

  3. Blank lines: Are there blank lines between your method definitions? Do blank lines separate logical groupings in the main method?

A few other things:

  1. Make sure there is space around operators and after commas.

  2. All of your methods should be declared using public static void. We’ll see shortly what these keywords mean.