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In the next module, you will learn how to compare column matrices for equality, how to compare two points for equality, how to compare two vectors forequality, how to add one column matrix to another, how to subtract one column matrix from another, and how to get a displacement vector from one point toanother.
This section contains a variety of miscellaneous information.
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Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
Complete listings of the programs discussed in this module are shown in Listing 26 through Listing 28 below.
Listing 26 . Source code for the game-math library class named GM2D02.
/*GM2D02.java
Copyright 2008, R.G.BaldwinRevised 02/03/08
The name GM2Dnn is an abbreviation for GameMath1Dnn.See the file named GM2D01.java for a general description
of this game-math library file. This file is an update ofGM2D01.
This update added the following new capabilities:Draw circles around points
Draw linesDraw vectors
Call a set method to change the values in aColMatrix object.
Call a set method to change the values in aPoint object.
Call a set method to change the values in aVector object.
Call a set method to change one of the pointsthat defines a line.
Constructors were updated to ensure that existing points,vectors, and lines are not corrupted by using the newset methods to change the values in the ColMatrix and/or
Point objects originally used to construct the points,vectors, and lines.
The updated constructors create and save clones of theColMatrix and/or Point objects originally used to define
the Point, Vector, and/or Line objects.Tested using JDK 1.6 under WinXP.
*********************************************************/import java.awt.geom.*;
import java.awt.*;public class GM2D02{
//An object of this class represents a 2D column matrix.// An object of this class is the fundamental building
// block for several of the other classes in the// library.
public static class ColMatrix{double[] data = new double[2];ColMatrix(double data0,double data1){//constructor
data[0]= data0;
data[1]= data1;
}//end constructor//--------------------------------------------------//public String toString(){
return data[0]+ "," + data[1];}//end overridden toString method
//--------------------------------------------------//public double getData(int index){if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
return data[index];
}//end else}//end getData method
//--------------------------------------------------//public void setData(int index,double data){if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
this.data[index]= data;
}//end else}//end setData method
//--------------------------------------------------//}//end class ColMatrix
//====================================================//public static class Point{GM2D02.ColMatrix point;Point(GM2D02.ColMatrix point){//constructor
//Create and save a clone of the ColMatrix object// used to define the point to prevent the point
// from being corrupted by a later change in the// values stored in the original ColMatrix object
// through use of its set method.this.point =
new ColMatrix(point.getData(0),point.getData(1));}//end constructor
//--------------------------------------------------//public String toString(){
return point.getData(0) + "," + point.getData(1);}//end toString
//--------------------------------------------------//public double getData(int index){if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
return point.getData(index);}//end else
}//end getData//--------------------------------------------------//public void setData(int index,double data){
if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
point.setData(index,data);}//end else
}//end setData//--------------------------------------------------////This method draws a small circle around the location
// of the point on the specified graphics context.public void draw(Graphics2D g2D){
Ellipse2D.Double circle =new Ellipse2D.Double(getData(0)-3,
getData(1)-3,6,
6);g2D.draw(circle);
}//end draw//--------------------------------------------------//
}//end class Point//====================================================//public static class Vector{
GM2D02.ColMatrix vector;Vector(GM2D02.ColMatrix vector){//constructor//Create and save a clone of the ColMatrix object
// used to define the vector to prevent the vector// from being corrupted by a later change in the
// values stored in the original ColMatrix object.this.vector = new ColMatrix(
vector.getData(0),vector.getData(1));}//end constructor
//--------------------------------------------------//public String toString(){
return vector.getData(0) + "," + vector.getData(1);}//end toString
//--------------------------------------------------//public double getData(int index){if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
return vector.getData(index);}//end else
}//end getData//--------------------------------------------------//public void setData(int index,double data){
if((index<0) || (index>1)){
throw new IndexOutOfBoundsException();}else{
vector.setData(index,data);}//end else
}//end setData//--------------------------------------------------////This method draws a vector on the specified graphics
// context, with the tail of the vector located at a// specified point, and with a small circle at the
// head.public void draw(Graphics2D g2D,GM2D02.Point tail){
Line2D.Double line = new Line2D.Double(tail.getData(0),
tail.getData(1),tail.getData(0)+vector.getData(0),
tail.getData(1)+vector.getData(1));//Draw a small circle to identify the head.
Ellipse2D.Double circle = new Ellipse2D.Double(tail.getData(0)+vector.getData(0)-2,
tail.getData(1)+vector.getData(1)-2,4,
4);g2D.draw(circle);
g2D.draw(line);}//end draw
//--------------------------------------------------//}//end class Vector
//====================================================////A line is defined by two points. One is called the// tail and the other is called the head.
public static class Line{GM2D02.Point[] line = new GM2D02.Point[2];Line(GM2D02.Point tail,GM2D02.Point head){
//Create and save clones of the points used to// define the line to prevent the line from being
// corrupted by a later change in the coordinate// values of the points.
this.line[0]= new Point(new GM2D02.ColMatrix(
tail.getData(0),tail.getData(1)));this.line[1] = new Point(new GM2D02.ColMatrix(head.getData(0),head.getData(1)));
}//end constructor//--------------------------------------------------//
public String toString(){return "Tail = " + line[0].getData(0) + ","+ line[0].getData(1) + "\nHead = "+ line[1].getData(0) + ","+ line[1].getData(1);}//end toString
//--------------------------------------------------//public GM2D02.Point getTail(){
return line[0];
}//end getTail//--------------------------------------------------//public GM2D02.Point getHead(){
return line[1];
}//end getHead//--------------------------------------------------//public void setTail(GM2D02.Point newPoint){
//Create and save a clone of the new point to// prevent the line from being corrupted by a
// later change in the coordinate values of the// point.
this.line[0]= new Point(new GM2D02.ColMatrix(
newPoint.getData(0),newPoint.getData(1)));}//end setTail
//--------------------------------------------------//public void setHead(GM2D02.Point newPoint){//Create and save a clone of the new point to
// prevent the line from being corrupted by a// later change in the coordinate values of the
// point.this.line[1] = new Point(new GM2D02.ColMatrix(newPoint.getData(0),newPoint.getData(1)));
}//end setHead//--------------------------------------------------//public void draw(Graphics2D g2D){
Line2D.Double line = new Line2D.Double(getTail().getData(0),
getTail().getData(1),getHead().getData(0),getHead().getData(1));
g2D.draw(line);}//end draw
//--------------------------------------------------//}//end class Line
//====================================================//}//end class GM2D02
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