Hey everyone, so this is my Turtle class:
(by the way, I am using the "Ready to Program with Java IDE" with the hsa console library methods)
// The "Turtle" class.
import java.awt.*;
import hsa.Console;
public class Turtle
{
static Console c;
protected int x, y, angle;
protected boolean showing = true;
protected Color clr = Color.black;
//Constructor for default initial values of position and angle.
public Turtle (Console C)
{
this.c = c;
x = c.getWidth () / 2;
y = c.getHeight () / 2;
angle = 0;
} //Default Turtle constructor.
//Alternate constructor.
public Turtle (Console C, int x, int y, int angle)
{
this.c = c;
this.x = x;
this.y = y;
this.angle = angle;
} //Alternate Turtle constructor
//Other methods of Turtle class
public void setColor (Color clr)
{
this.clr = clr;
} //setColor method
public void setPosition (int x, int y)
{
this.x = x;
this.y = y;
} //setPosition method
public void setAngle (int angle)
{
this.angle = angle;
} //setAngle method
public void turnLeft (int turnAngle)
{
angle += turnAngle;
angle = angle % 360;
} //turnLeft method
public void turnRight (int turnAngle)
{
angle -= turnAngle;
angle = angle % 360;
} //turnRight method
public void showTrace ()
{
showing = true;
} //showTrace method
public void hideTrace ()
{
showing = false;
} //hideTrace method
public void move (int distance)
{
int newx, newy;
double rAngle = (angle * Math.PI) / 180;
c.println (angle);
newx = (int) Math.round (x + Math.cos (rAngle) * distance);
newy = (int) Math.round (y - Math.cos (rAngle) * distance);
if (showing)
{
c.setColor (clr);
c.drawLine (x, y, newx, newy);
}
x = newx;
y = newy;
} //move method
} // Turtle class
okay and this is my separate java file where i use the above class:
// The "UseTurtle" class.
import java.awt.*;
import hsa.Console;
public class UseTurtle
{
static Console c; // The output console
public static void main (String[] args)
{
c = new Console ();
Turtle t = new Turtle(c);
} // main method
} // UseTurtle class
all i did was create the object. when i run the program, I get the following error:
java.lang.NullPointerException
at Turtle.<init>(Turtle.java:19)
at UseTurtle.main(UseTurtle.java:13)
any help please?
