teaching machines

CS 245 Lecture 10 – Abstract Classes

October 3, 2013 by Chris Johnson. Filed under cs245, fall 2013, lectures.

Agenda

• what ?s
• the inheritance spectrum
• abstract classes
• writing a travel diary with Google Earth

TODO

• Read on Generics in chapter 12 through section 12.3 in Core Java. 1/4 sheet.

Travel Diary

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>
<Style id="seethrough"><PolyStyle><color>7fffffff</color></PolyStyle></Style>

<Placemark>
<name>Eurasian Smoketree</name>
<description>This tree is surreal. <img src="smoketree.jpg" /></description>
<Point>
<coordinates> -93.65057870772075,42.03081012742565</coordinates>
</Point>
</Placemark>

<Placemark>
<name>Triangle of Fate</name>
<description>At all costs, avoid traveling the unmarked edge of this triangle during the fall.  A female ginkgo lies on that edge, and female ginkgos are some of stinkiest trees known to man.<img src="ginkgo.jpg" /></description>
<LineString>
<tesselate>1</tesselate>
<coordinates> -93.65014025291298,42.02556822761216 -93.65031285507688,42.02551563374377 -93.65031551056221,42.0257240592268</coordinates>
</LineString>
</Placemark>

<Placemark>
<name>Baldcypress Alley</name>
<description>I love baldcypress trees.  They do not fit cleanly into an inheritance hierarchy, because they are both deciduous and coniferous.<img src="baldcypress.jpg" /></description>
<styleUrl>#seethrough</styleUrl>
<Polygon>
<outerBoundaryIs>
<LinearRing>
<coordinates> -93.65289780478878,42.03059860529465 -93.6529014382725,42.03049484516234 -93.65207503713377,42.03049447620213 -93.65208168225243,42.03059931197005</coordinates>
</LinearRing>
</outerBoundaryIs>
</Polygon>
</Placemark>

</Document>
</kml>

Code

TravelDiary.java

package lecture10;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;

public class TravelDiary { 
  private ArrayList<Placemark> placemarks;
  
  public TravelDiary() {
    placemarks = new ArrayList<Placemark>();
  }
  
  public void add(Placemark placemark) {
    placemarks.add(placemark);
  }
  
  public void writeKML(String path) throws FileNotFoundException {
    PrintWriter out = new PrintWriter(path);
    
    out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
    out.println("<kml xmlns=\"http://www.opengis.net/kml/2.2\">");
    out.println("<Document>");
    out.println("<Style id=\"seethrough\"><PolyStyle><color>7fffffff</color></PolyStyle></Style>\n");

    for (Placemark placemark : placemarks) {
      out.println(placemark.toKML());
    }
    
    out.println("</Document>");
    out.println("</kml>");
    
    out.close();
  }
}

Placemark.java

package lecture10;

import java.util.ArrayList;

public abstract class Placemark {
  private String name;
  private String description;
  private ArrayList<LatLon> coordinates;
  
  public Placemark(String name, String description) {
    this.name = name;
    this.description = description;
    coordinates = new ArrayList<LatLon>();
  }
  
  public void addCoordinate(LatLon coord) {
    coordinates.add(coord);
  }
  
  public String toKML() {
    String s = "<Placemark>\n";
    s += "<name>" + name + "</name>\n";
    s += "<description>" + description + "</description>\n";
    s += getSpecializedKML();
    s += "</Placemark>\n";
    return s;
  }
  
  public String getCoordinatesTag() {
    String s = "<coordinates>";
    for (LatLon c : coordinates) {
      s += c + " ";
    }
    s += "</coordinates>\n";
    return s;
  }
  
  public abstract String getSpecializedKML();
}

LatLon.java

package lecture10;

public class LatLon {
  private double lat;
  private double lon;
  
  public LatLon(double lat,
                double lon) {
    this.lat = lat;
    this.lon = lon;
  }

  public double getLat() {
    return lat;
  }

  public double getLon() {
    return lon;
  }
  
  public String toString() {
    return lat + "," + lon;
  }
}

PinPlacemark.java

package lecture10;

public class PinPlacemark extends Placemark {
  
  public PinPlacemark(String name, String description) {
    super(name, description);
  }
  
  @Override
  public String getSpecializedKML() {
    String s = "<Point>\n";
    s += getCoordinatesTag();
    s += "</Point>\n";
    return s;
  }
}

LinePlacemark.java

package lecture10;

public class LinePlacemark extends Placemark {
  public LinePlacemark(String name,
                       String description) {
    super(name, description);
  }

  @Override
  public String getSpecializedKML() {
    String s = "<LineString>\n<tesselate>1</tesselate>\n";
    s += getCoordinatesTag();
    s += "</LineString>\n";
    return s;
  }
}

RegionPlacemark.java

package lecture10;

public class RegionPlacemark extends Placemark {
  public RegionPlacemark(String name,
                         String description) {
    super(name, description);
  }

  @Override
  public String getSpecializedKML() {
    String s = "<styleUrl>#seethrough</styleUrl>\n";
    s += "<Polygon>\n<outerBoundaryIs>\n<LinearRing>\n";
    s += getCoordinatesTag();
    s += "</LinearRing>\n</outerBoundaryIs>\n</Polygon>\n";
    return s;
  }
}

Main.java

package lecture10;

import java.io.FileNotFoundException;

public class Main {
  public static void main(String[] args) throws FileNotFoundException {
    TravelDiary diary = new TravelDiary();

    // Cannot create instances of abstract things.
    // new Placemark("Foo", "Boo");

    PinPlacemark pin = new PinPlacemark("Eurasian Smoketree",
                                        "This tree is surreal. <img src=\"smoketree.jpg\" />");
    pin.addCoordinate(new LatLon(-93.65057870772075, 42.03081012742565));
    diary.add(pin);

    LinePlacemark line = new LinePlacemark("Triangle of Fate", "At all costs, avoid traveling the unmarked edge of this triangle during the fall.  A female ginkgo lies on that edge, and female ginkgos are some of stinkiest trees known to man.<img src=\"ginkgo.jpg\" />");
    line.addCoordinate(new LatLon(-93.65014025291298, 42.02556822761216));
    line.addCoordinate(new LatLon(-93.65031285507688, 42.02551563374377));
    line.addCoordinate(new LatLon(-93.65031551056221, 42.0257240592268));
    diary.add(line);

    RegionPlacemark region = new RegionPlacemark("Baldcypress Alley",
                                                 "I love baldcypress trees.  They do not fit cleanly into an inheritance hierarchy, because they are both deciduous and coniferous.<img src=\"baldcypress.jpg\" />");
    region.addCoordinate(new LatLon(-93.65289780478878, 42.03059860529465));
    region.addCoordinate(new LatLon(-93.6529014382725, 42.03049484516234));
    region.addCoordinate(new LatLon(-93.65207503713377, 42.03049447620213));
    region.addCoordinate(new LatLon(-93.65208168225243, 42.03059931197005));
    diary.add(region);

    diary.writeKML(System.getProperty("user.home") + "/Desktop/inclass_diary.kml");
  }
}

Haiku