// SquareTurtle Demo Program

// this program illustrates two different ways of drawing squares with a Turtle

// 1. adding the static method to the client program and passing a Turtle object
// as a parameter. 

// The call statement     drawSquare(donny);     passes donny
// as an actual parameter. donny plugs in for anyTurtle which is a formal
// parameter in the static method.

// 2. typing out a whole class named SquareTurtle that includes a drawSquare
// instance method. 

// Because leo is declared & instantiated as a SquareTurtle, 
// the call statement      leo.drawSquare();      passes leo as an implied
// parameter to the drawSquare method that is found in the SquareTurtle class.
// The optional keyword this is used to refer to leo since he is implied
// parameter that was passed.
// Notice how the class SquareTurtle extends the Turtle class
// This is called inheritance and it saves time by making all of the methods
// in Turtle (and SimpleTurtle) available for use by SquareTurtle's!

// For certain tasks, "static" methods are preferable. But usually it is better
// to create a whole new class that contains an "instance" method. The 
// drawSquare method is much more reusable BY OTHER CLIENT PROGRAMMERS 
// if it is packaged into a separate class that can be distributed and even
// posted online as external class folders and jar files. Static methods are 
// not very reusable since the other client programmer would need access to
// the source code of the original client program in order to copy and paste
// the code. In the real world, client programmers do not share their client
// program source code with other client programmers. But class files like
// SquareTurtle are distributed or even sold along with their API documentation
// to client programmers.


////////////////// CLIENT PROGRAM ////////////////////////////////////////////
public class SquareTurtleDemo
{
    public static void main(String[] args)
    {
        World earth = new World();
        Turtle donny = new Turtle(50, 250, earth);
        SquareTurtle leo = new SquareTurtle(100, 100, earth);
        
        drawSquare(donny);  // not a great way to draw a square
        
        leo.drawSquare();   // better way to draw a square
    }
    
    // draw a square
    public static void drawSquare(Turtle anyTurtle)
    {
        anyTurtle.penDown();
        anyTurtle.forward();
        anyTurtle.turnRight();
        anyTurtle.forward();
        anyTurtle.turnRight();
        anyTurtle.forward();
        anyTurtle.turnRight();
        anyTurtle.forward();       
    }
    
}

//////////////// SQUARE TURTLE CLASS /////////////////////////////////////////
// pretend this is in a different java source file named SquareTurtle.java
// if the keyword public is removed, you can be lazy and type multiple classes
// in the same file as a client program that has a main method. I only do this
// to make it easier to post examples on my website and to save paper when
// printing worksheets.

class SquareTurtle extends Turtle
{
    // constructor (required, we will study constructors later)
    public SquareTurtle(int x, int y, ModelDisplay display)
    {
        super(x, y, display); // super means that you are calling a constructor
    }                         // in the parent class (Turtle)

    // draw a square
    public void drawSquare()
    {
        this.penDown();
        this.forward();
        this.turnRight();
        this.forward();
        this.turnRight();
        this.forward();
        turnRight();        // using the keyword    this     is optional
        forward();
    }
    
}