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Vector.java
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Vector.java
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import greenfoot.Greenfoot;
/**
* A 2D vector.
*
* @author Poul Henriksen
* @author Michael Kolling
*
* @version 2.0
*/
public final class Vector
{
double dx;
double dy;
int direction;
double length;
/**
* Create a new, neutral vector.
*/
public Vector()
{
}
/**
* Create a vector with given direction and length. The direction should be in
* the range [0..359], where 0 is EAST, and degrees increase clockwise.
*/
public Vector(int direction, double length)
{
this.length = length;
this.direction = direction;
updateCartesian();
}
/**
* Create a vector by specifying the x and y offsets from start to end points.
*/
public Vector(double dx, double dy)
{
this.dx = dx;
this.dy = dy;
updatePolar();
}
/**
* Set the direction of this vector, leaving the length intact.
*/
public void setDirection(int direction)
{
this.direction = direction;
updateCartesian();
}
/**
* Add another vector to this vector.
*/
public void add(Vector other)
{
dx += other.dx;
dy += other.dy;
updatePolar();
}
/**
* Set the length of this vector, leaving the direction intact.
*/
public void setLength(double length)
{
this.length = length;
updateCartesian();
}
/**
* Scale this vector up (factor > 1) or down (factor < 1). The direction
* remains unchanged.
*/
public void scale(double factor)
{
length = length * factor;
updateCartesian();
}
/**
* Set this vector to the neutral vector (length 0).
*/
public void setNeutral() {
dx = 0.0;
dy = 0.0;
length = 0.0;
direction = 0;
}
/**
* Revert to horizontal component of this movement vector.
*/
public void revertHorizontal() {
dx = -dx;
updatePolar();
}
/**
* Revert to vertical component of this movement vector.
*/
public void revertVertical() {
dy = -dy;
updatePolar();
}
/**
* Return the x offset of this vector (start to end point).
*/
public double getX() {
return dx;
}
/**
* Return the y offset of this vector (start to end point).
*/
public double getY() {
return dy;
}
/**
* Return the direction of this vector (in degrees). 0 is EAST.
*/
public int getDirection() {
return direction;
}
/**
* Return the length of this vector.
*/
public double getLength() {
return length;
}
/**
* Update the direction and length fom the current dx, dy.
*/
private void updatePolar()
{
this.direction = (int) Math.toDegrees(Math.atan2(dy, dx));
this.length = Math.sqrt(dx*dx+dy*dy);
}
/**
* Update dx and dy from the current direction and length.
*/
private void updateCartesian()
{
dx = length * Math.cos(Math.toRadians(direction));
dy = length * Math.sin(Math.toRadians(direction));
}
/**
* Return a copy of this vector.
*/
public Vector copy()
{
Vector copy = new Vector();
copy.dx = dx;
copy.dy = dy;
copy.direction = direction;
copy.length = length;
return copy;
}
}