Lab 7: Vtable and Java Game

1. VTable
   1. Create vtable.cc

      class A {
      private:
      	int a;
      public:
      	virtual void f1(void) {
      	}
      };
      
      class B : public A {
      private:
      	int b;
      public:
      	virtual void f2(void) {
      	}
      };
      
      int main(void) {
      	return (0);
      }
      	

   2. Compile vtable.cc

      $ g++ -fdump-class-hierarchy vtable.cc
          

   3. Read vtable.cc.t01.class
   
   
   
2. Java Game
   1. Download pa3.tgz
   2. Ungzip and untar it
   3. Create Laser.java

      // An example code to demonstrate how to use the GameSpace and Vector class.
      
      // Need to import below for the Vector class
      import java.util.*;
      
      class Laser extends GameSpace {
          // Constructor
          public Laser(int w, int h, int num) {
      	super(w, h);
      	_num = num;
          }
          
          // The main function
          public static void main(String[] args) {
      	// Check for the command line arguments
      	if (args.length != 1) {
      	    System.err.println("Usage: java Laser num");
      	    System.exit(-1);
      	}
      	// Instantiate a Laser object and then run it
      	newLaser(args[0]).run();
          }
          
          // Return a new Laser class
          private static Laser newLaser(String num) {
      	return (new Laser(600, 400, Integer.parseInt(num)));
          }
          
          // The sleep function
          private void sleep(int ms) {
      	try {
      	    Thread.sleep(ms);
      	} catch (InterruptedException e) {
      	}
          }
          
          // The main loop
          public void run() {
      	while (true) {
      	    // Randomly generate a number of lines
      	    for (int i = 0; i < _num; i++) {
      		int x1 = (int)(Math.random() * 600);
      		int y1 = (int)(Math.random() * 400);
      		int x2 = (int)(Math.random() * 600);
      		int y2 = (int)(Math.random() * 400);
      		cLines.push_back(new Line(this, x1, y1, x2, y2));
      	    }
      	    // Draw the lines
      	    cLines.draw();
      	    // Clear the lines
      	    cLines.clear();
      	    // Update the canvas
      	    nextTimeStep();
      	    // Pause for 100ms
      	    sleep(100);
      	}
          }
          
          // A private line class
          class Line {
      	private Laser _cLaser = null;
      	private int _x1, _y1, _x2, _y2;
      	Line(Laser cLaser, int x1, int y1, int x2, int y2) {
      	    _cLaser = cLaser;
      	    _x1 = x1;
      	    _y1 = y1;
      	    _x2 = x2;
      	    _y2 = y2;
      	}
      	// A class should know how to draw itself!!!
      	public void draw() {
      	    _cLaser.drawLine(_x1, _y1, _x2, _y2, 1.0f, 0.0f, 0.0f);
      	}
          }
          
          // A private class to keep track of a collection of lines
          class Lines extends Vector<Line> {
      	public void push_back(Line l) {
      	    add(l);
      	}
      	public void draw() {
      	    for (int i = 0; i < size(); i++) {
      		get(i).draw();
      	    }
      	}
          }
          
          private int _num = 0;                // Batch of lines
          private Lines cLines = new Lines();  // A collection of lines
      }
      	

   4. Compile Laser.java and run it.

      $ javac Laser.java
      $ java Laser 10
      	

   5. Now, create Tank.java, load the first tank image, tank0.gif, and have your code to take four parameters: x, y, speed and angle (in degree) from the command line. Compute the correct location for the tank on each frame. Hint: look at the extracode.java
   6. When the above is done, try to load all the tank images, use the correct image based on the angle provided.

References:

• VTable examples