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Listing 20 . Source code for the program named VectorAdd01.
/*VectorAdd01.java
Copyright 2008, R.G.BaldwinRevised 02/10/08
This program illustrates the addition of two or morevectors. It also illustrates the Head-to-Tail rule
described by Kjell.Tested using JDK 1.6 under WinXP.
*********************************************************/import java.awt.*;
import javax.swing.*;import java.awt.geom.*;
class VectorAdd01{
public static void main(String[]args){
GUI guiObj = new GUI();}//end main
}//end controlling class VectorAdd01//======================================================//
class GUI extends JFrame{//Specify the horizontal and vertical size of a JFrame
// object.int hSize = 275;
int vSize = 200;Image osi;//an off-screen image
int osiWidth;//off-screen image widthint osiHeight;//off-screen image height
MyCanvas myCanvas;//a subclass of CanvasGUI(){//constructor//Set JFrame size, title, and close operation.
setSize(hSize,vSize);setTitle("Copyright 2008,Baldwin");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//Create a new drawing canvas and add it to the// center of the JFrame.
myCanvas = new MyCanvas();this.getContentPane().add(myCanvas);//This object must be visible before you can get an
// off-screen image. It must also be visible before// you can compute the size of the canvas.
setVisible(true);osiWidth = myCanvas.getWidth();
osiHeight = myCanvas.getHeight();//Create an off-screen image and get a graphics
// context on it.osi = createImage(osiWidth,osiHeight);
Graphics2D g2D = (Graphics2D)(osi.getGraphics());//Draw some graphical objects on the off-screen// image that represent underlying data objects in
// 2D space.drawOffScreen(g2D);
//Cause the overridden paint method belonging to// myCanvas to be executed.
myCanvas.repaint();}//end constructor
//----------------------------------------------------////The purpose of this method is to add some Vector// objects and to cause visual manifestations of the raw
// Vector objects and the resultant Vector objects to be// drawn onto an off-screen image.
void drawOffScreen(Graphics2D g2D){//Translate the origin on the off-screen// image and draw a pair of orthogonal axes on it.
setCoordinateFrame(g2D);//Define two vectors.GM2D04.Vector vecA = new GM2D04.Vector(
new GM2D04.ColMatrix(50,100));GM2D04.Vector vecB = new GM2D04.Vector(
new GM2D04.ColMatrix(75,25));//Define a third vector as the sum of the first// two vectors defined above.
GM2D04.Vector sumOf2 = vecA.add(vecB);//Draw vecA in RED with its tail at the origing2D.setColor(Color.RED);
vecA.draw(g2D,new GM2D04.Point(new GM2D04.ColMatrix(0,0)));//Draw vecB in GREEN with its tail at the head of vecA
g2D.setColor(Color.GREEN);vecB.draw(g2D,new GM2D04.Point(new GM2D04.ColMatrix(
vecA.getData(0),vecA.getData(1))));//Draw sumOf2 in MAGENTA with its tail at the origin.// The head will coincide with the head of vecB.
g2D.setColor(Color.MAGENTA);sumOf2.draw(g2D,new GM2D04.Point(new GM2D04.ColMatrix(
0.0,0.0)));//Now define another vector and add it to vecA and
// vecB.GM2D04.Vector vecC = new GM2D04.Vector(
new GM2D04.ColMatrix(30,-150));//Draw vecD in BLUE with its tail positioned at the// sum of vecA and vecB
g2D.setColor(Color.BLUE);vecC.draw(g2D,new GM2D04.Point(new GM2D04.ColMatrix(
sumOf2.getData(0),sumOf2.getData(1))));//Define a vector as the sum of vecA, vecB, and vecCGM2D04.Vector sumOf3 = (vecA.add(vecB)).add(vecC);
//Draw sumOf3 in BLACK with its tail at the origin.g2D.setColor(Color.BLACK);
sumOf3.draw(g2D,new GM2D04.Point(new GM2D04.ColMatrix(0.0,0.0)));
}//end drawOffScreen//----------------------------------------------------//
//This method is used to set the origin to a point near// the upper-left corner of the off-screen image and
// draw orthogonal axes on the off-screen image. There// is no intention to perform mathematical operations on
// the axes, so they are drawn independently of the// classes and methods in the game-math library using
// the simplest method available for drawing a line.private void setCoordinateFrame(Graphics2D g2D){
//Translate the origin.g2D.translate(0.2*osiWidth,0.2*osiHeight);//Draw new X and Y-axes in default BLACK
g2D.drawLine(-(int)(0.2*osiWidth),0,(int)(0.8*osiWidth),0);g2D.drawLine(0,-(int)(0.2*osiHeight),
0,(int)(0.8*osiHeight));}//end setCoordinateFrame method//====================================================////This is an inner class of the GUI class.class MyCanvas extends Canvas{
//Override the paint() method. This method will be// called when the JFrame and the Canvas appear on the
// screen or when the repaint method is called on the// Canvas object.
//The purpose of this method is to display the// off-screen image on the screen.
public void paint(Graphics g){g.drawImage(osi,0,0,this);
}//end overridden paint()}//end inner class MyCanvas}//end class GUI//======================================================//
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