Page 269 - The Definitive Guide to Building Java Robots

Preston_5564C07.fm Page 250 Monday, September 26, 2005 5:38 AM

250 CHAPTER 7 ■ NAVIGATION

} else {
if (a.x < b.x) {
d = 90 - d;
} else {
d = 180 + (90 - d);
}
}
return new DistanceVector(d, mag);
}
Next, I want to create a data structure with a name I could store and recall at a later time.
I can’t do this with a Point, but I can reuse a Point by just extending it and giving my new class
a variable called name. I called this class NavPoint and added the string name to its
constructor. See Example 7-12.

Example 7-12. NavPoint.java
package com.scottpreston.javarobot.chapter7;

import java.awt.Point;

public class NavPoint extends Point {

public static final String START_POINT = "start";
public static final String EXIT_POINT = "exit";
public static final String CENTER_POINT = "center";

public String name = null;

public NavPoint(String name) {
super();
this.name = name;
}

public NavPoint(String name, int x, int y) {
super(x, y);
this.name = name;
}
public NavPoint(String name, Point p) {
super(p);
this.name = name;
}
}

Next, it’s time for the robot to figure out its start position on its own.