Questions on HW8-Sp2005

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File: C:\cs1316\java-source\Immigrant.java  [line: 9]
Error: cannot resolve symbol
symbol  : constructor Agent ()
location: class Agent

public class Immigrant extends Agent {

  /** 
   * Open a frame sequence at the given directory
   * @param dir String where the directory is
   **/
  public void openFrames(String dir){
    frames = new FrameSequence(dir);
  }

Error: non-static method openFrames(java.lang.String) cannot be referenced from a static context

Error: cannot resolve symbol
symbol  : variable frames 
location: class Simulation

java.lang.NoSuchMethodError: World.setAutoRepaint(Z)V
  at ImmigrationSimulation.setUp(ImmigrationSimulation.java:23)
  at Simulation.run(Simulation.java:88)
  at Simulation.run(Simulation.java:117)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  at java.lang.reflect.Method.invoke(Unknown Source) 

/**
   * Method to set the automatically repaint flag
   * @param value if true will auto repaint 
   */
  public void setAutoRepaint(boolean value) 
  { 
    autoRepaint = value; 
  } 

 public void setUp(){
    // Let the world be set up
    //super.setUp();
    // Set it up with a smaller world
    world = new World(400,400);
    world.setAutoRepaint(false); 

   public String lineForFile(){
    PersonAgent first;
    first = (PersonAgent) agents.get(0);
    return (new Integer(first.infected())).toString();
  }

Most common errors I'm seeing:

• People are creating an immigrate()/emigrate() function to handle moving people across the Atlantic. They call it once when they figure out that people should go into transit, but never again! You probably need something like this:

  public void act(){
  //** MARK ADDITION
  if (transit) {immigrate(); return;}/** So that immigrate gets called as long as in transit

• I'm seeing people test for overcrowding by having a variable that they count up from 0, and when it gets to 3, we declare that it's overcrowded and wants to emigrate. What I'm not seeing is, if the number of neigbors is less than five overcrowding = 0;, because we only care about 3 steps in a row where there is overcrowding.
• People are getting hung up on moving exactly 33 steps per stage of transit, and the code is getting hard to read. Here's an immigrate() method that I helped someone with (I've done this three times now, and it looks very similar each time) that explicitly says "Move to 170, then 140, then 100" which makes it much easier to code.

  public void immigrate() { //** TWEAKED BY MARK
    transit = true;
    int myX = this.getXPos();
    if (myX > 199) //if in Europe
    { // ***Call this first step
      this.setBodyColor(Color.yellow); //Color is YELLOW if in-transit
      this.moveTo(170,this.getYPos());}
      if (myX == 170){
      //*** Call this the second step
       this.moveTo(140,this.getYPos());}
      if (myX==140){
      //*** Step 3: Arrive in America
      this.moveTo(100,this.getYPos());
      transit = false;
      American = true; // Though instance variables shouldn't be capitalized...
      this.setBodyColor(Color.blue); // Or whatever color you want Americans to be
      }
      if(randNumGen.nextInt(10) == 1)//10% of dying in Atlantic Ocean
        {this.die();}
    }

• Mark Guzdial

> 200 + (200 * Math.random())
298.0137462449052
> (int) (200 + (200 * Math.random()))
376

• Mark Guzdial

• erin

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• Homeworks-Spring 2005 last edited on 22 April 2005 at 1:28 pm by lawn-199-77-215-13.lawn.gatech.edu