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What's next?

In the next module you will learn how to use the game-math library for translation and animation in two dimensions.

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: GAME 2302-0125: Vector Addition
  • File: Game0125.htm
  • Published: 10/15/12
  • Revised: 02/02/16
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Complete program listings

Complete listings of the programs discussed in this module are shown in Listing 19 through Listing 24 below.

Listing 19 . Source code for the game-math library named GM2D04.

/*GM2D04.java Copyright 2008, R.G.BaldwinRevised 02/08/08 The name GM2Dnn is an abbreviation for GameMath2Dnn.See the file named GM2D01.java for a general description of this game-math library file. This file is an update ofGM2D03. This update added the following new capabilities:Vector addition - Adds this Vector object to a Vector object received as an incoming parameter and returns thesum as a resultant Vector object. Added a method named getLength that returns the lengthof a vector as type double. Added a method named addVectorToPoint to add a Vector toa Point producing a new Point. Tested using JDK 1.6 under WinXP.*********************************************************/ import java.awt.geom.*;import java.awt.*; public class GM2D04{//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];public ColMatrix(double data0,double data1){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 //--------------------------------------------------////This method overrides the equals method inherited// from the class named Object. It compares the values // stored in two matrices and returns true if the// values are equal or almost equal and returns false // otherwise.public boolean equals(Object obj){ if(obj instanceof GM2D04.ColMatrix&&Math.abs(((GM2D04.ColMatrix)obj).getData(0) - getData(0))<= 0.00001&&Math.abs(((GM2D04.ColMatrix)obj).getData(1) - getData(1))<= 0.00001){ return true;}else{ return false;}//end else}//end overridden equals method //--------------------------------------------------////Adds one ColMatrix object to another ColMatrix // object, returning a ColMatrix object.public GM2D04.ColMatrix add(GM2D04.ColMatrix matrix){ return new GM2D04.ColMatrix(getData(0)+matrix.getData(0), getData(1)+matrix.getData(1));}//end subtract //--------------------------------------------------////Subtracts one ColMatrix object from another// ColMatrix object, returning a ColMatrix object. The // object that is received as an incoming parameter// is subtracted from the object on which the method // is called.public GM2D04.ColMatrix subtract( GM2D04.ColMatrix matrix){return new GM2D04.ColMatrix( getData(0)-matrix.getData(0),getData(1)-matrix.getData(1)); }//end subtract//--------------------------------------------------// }//end class ColMatrix//====================================================//public static class Point{ GM2D04.ColMatrix point;public Point(GM2D04.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//--------------------------------------------------////Returns a reference to the ColMatrix object that // defines this Point object.public GM2D04.ColMatrix getColMatrix(){ return point;}//end getColMatrix //--------------------------------------------------////This method overrides the equals method inherited // from the class named Object. It compares the values// stored in the ColMatrix objects that define two // Point objects and returns true if they are equal// and false otherwise. public boolean equals(Object obj){if(point.equals(((GM2D04.Point)obj). getColMatrix())){return true; }else{return false; }//end else}//end overridden equals method//--------------------------------------------------// //Gets a displacement vectorfrom one Point object to // a second Point object. The vector points from the// object on which the method is called to the object // passed as a parameter to the method. Kjell// describes this as the distance you would have to // walk along the x and then the y axes to get from// the first point to the second point. public GM2D04.Vector getDisplacementVector(GM2D04.Point point){ return new GM2D04.Vector(new GM2D04.ColMatrix(point.getData(0)-getData(0), point.getData(1)-getData(1)));}//end getDisplacementVector //--------------------------------------------------////Adds a Vector to a Point producing a new Point.public GM2D04.Point addVectorToPoint( GM2D04.Vector vec){return new GM2D04.Point(new GM2D04.ColMatrix( getData(0) + vec.getData(0),getData(1) + vec.getData(1))); }//end addVectorToPoint//--------------------------------------------------// }//end class Point//====================================================//public static class Vector{ GM2D04.ColMatrix vector;public Vector(GM2D04.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 ColVector 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,GM2D04.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 //--------------------------------------------------////Returns a reference to the ColMatrix object that// defines this Vector object. public GM2D04.ColMatrix getColMatrix(){return vector; }//end getColMatrix//--------------------------------------------------// //This method overrides the equals method inherited// from the class named Object. It compares the values // stored in the ColMatrix objects that define two// Vector objects and returns true if they are equal // and false otherwise.public boolean equals(Object obj){ if(vector.equals(((GM2D04.Vector)obj).getColMatrix())){ return true;}else{ return false;}//end else}//end overridden equals method //--------------------------------------------------////Adds this vector to a vector received as an incoming// parameter and returns the sum as a vector. public GM2D04.Vector add(GM2D04.Vector vec){return new GM2D04.Vector(new ColMatrix( vec.getData(0)+vector.getData(0),vec.getData(1)+vector.getData(1))); }//end add//--------------------------------------------------////Returns the length of a Vector object. public double getLength(){return Math.sqrt( getData(0)*getData(0) + getData(1)*getData(1));}//end getLength //--------------------------------------------------//}//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{ GM2D04.Point[]line = new GM2D04.Point[2];public Line(GM2D04.Point tail,GM2D04.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 GM2D04.ColMatrix(tail.getData(0),tail.getData(1))); this.line[1]= new Point(new GM2D04.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 GM2D04.Point getTail(){return line[0];}//end getTail //--------------------------------------------------//public GM2D04.Point getHead(){return line[1];}//end getHead //--------------------------------------------------//public void setTail(GM2D04.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 GM2D04.ColMatrix(newPoint.getData(0),newPoint.getData(1))); }//end setTail//--------------------------------------------------//public void setHead(GM2D04.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 GM2D04.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 GM2D04 //======================================================//

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