Source code in the processing programming language

// define a rudimentary class
class HelloWorld
{
    public static void sayHello()
    {
        println("Hello, world!");
    }
    public void sayGoodbye()
    {
        println("Goodbye, cruel world!");
    }
}

// call the class method
HelloWorld.sayHello();

// create an instance of the class
HelloWorld hello = new HelloWorld();

// and call the instance method
hello.sayGoodbye();