Ok I finished the code but the thing is still not rotating. i have compared my code to other people's and I did everything that the book said I should do and it's still not rotating!! please help!! It says no syntax errors for me by the way.
import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
import java.util.*;
/**
* A 'Body' is any kind of object in space that has a mass. It could be a star, or a planet,
* or anything else that floats around in space.
*
* @author Michael Kolling
* @version 0.1
*/
public class Body extends SmoothMover
{
// constants
private static final double GRAVITY = 5.8;
private static final Color defaultColor = new Color(255, 216, 0);
// fields
private double mass;
/**
* Construct a Body with default size, mass, movement and color.
*/
public Body()
{
this (20, 300, new Vector(0, 1.0), defaultColor);
}
/**
* Construct a Body with a specified size, mass, movement and color.
*/
public Body(int size, double mass, Vector movement, Color color)
{
mass = mass;
addForce(movement);
GreenfootImage image = new GreenfootImage (size, size);
image.setColor (color);
image.fillOval (0, 0, size-1, size-1);
setImage (image);
}
/**
* Act. That is: apply the gravitation forces from
* all other bodies around, and then move.
*/
public void act()
{
applyForces();
move();
// To be done - not yet implemented
}
/**
* Return the mass of this body.
*/
public double getMass()
{
return mass;
}
private void applyForces()
{
List<Body> bodies = getWorld().getObjects(Body.class);
for (Body body : bodies)
{
if (body != this)
{
applyGravity (body);
}
}
}
private void applyGravity(Body other)
{
double dx = other.getExactX() - this.getExactX();
double dy = other.getExactY() - this.getExactY();
Vector force = new Vector (dx, dy);
double distance = Math.sqrt (dx * dx + dy * dy);
double strength = GRAVITY * this.mass * other.mass /
(distance * distance);
double acceleration = strength / this.mass;
force.setLength (acceleration);
addForce (force);
}
}