Animals, Vehicles, Houses, Shapes

class GraphicsCircle
  extends Circle
{
  GraphicsCircle(double nx, double ny, double nr)
  {
    super(nx,ny,nr);
  }
  boolean isOnScreen = false;
  void draw(DrawWindow w)
  {
    w.drawCircle(x, y, radius, outline, noFill);
  }
}

class Object
{
  Object()
  Object clone () // component copy
  boolean equals(Object o) // component equality
  String toString() // gives String image of object
  void finalize() // done when object is freed
  Class getClass() // gives run-time class of an object
  int hashCode() // allows use in a Hashtable
}

class FilledCircle
  extends GraphicsCircle
{
  void draw(DrawWindow w)
  {
    if (!do_fill)
      super.draw(w); // calls GraphicsCircle.draw() on this
    else
      w.drawCircle(x,y,radius, outline, fill);
  }
}

Circle c = new FilledCircle();
c.draw(); // calls FilledCircle.draw()
c = new GraphicsCircle(...);
c.draw(); // calls GraphicsCircle.draw()

Circle C = new FilledCircle();
FilledCircle f = (FilledCircle)C; // throws ClassCastException if C is not FilledCircle
if (C instanceof FilledCircle) // checking actual type is wise
  f = (FilledCircle)C;

ArrayList l = new ArrayList(10);
l.insert( new FilledCircle() );
Object x = l.remove();
FilledCircle c = (FilledCircle)x;

abstract class Shape
{
  abstract double area();
  abstract double circumference(); 
} 
class Circle
  extends Shape
{

...
double area() { return ...;}
double circumference() { return ...; }

}

class Shape
{
  abstract double area();
  abstract double circumference(); 
  static double sumArea(Shape[] a)
  {
    double total = 0.0;
    for (int i=0; i < a.length; i++)
      total += a[i].area();
    return total;
  }
} 

Shape[] a = {new Circle(...), new Square(...), new GraphicsCircle(...)};
double totalArea = Shape.sumArea(a);

public class Shape
{
  protected Point origin;
  protected Color color;
  Shape(Point newOrigin, Color newColor)
  {
    origin = newOrigin;
    color = newColor;
  }
  public void moveTo(Point to)
  {
    origin = to;
  }
}

public class Circle
  extends Shape
{
  private static final double PI = 3.14159;
  protected double radius;
  public Circle( double newRadius, Point newOrigin, Color newColor )
  {
    super( newOrigin, newColor );
    radius = newRadius;
  }
  // inherits moveTo from Shape
  public double circumference()
  {
    return 2.0 * PI * radius;
  }
}

abstract class Shape
{
  public abstract double area();
}

class Triangle
  extends Shape
{
  protected double base;
  protected double height;
  public Triangle( double newBase, double newHeight )
  {
    base = newBase;
    height = newHeight;
  }
  public double area()
  {
    return base * height / 2.0;
  }
}

class Square
  extends Shape
{
  protected double side;
  public Square( double newSide )
  {
    side = newSide;
  }
  public double area()
  {
    return side * side;
  }
}

class ListNode
{
  Shape info;
  ListNode next;
  ListNode( Shape newInfo, ListNode newNext )
  {
    info = newInfo;
    next = newNext;
  }
}

class Picture
{
  ListNode head;
  Picture()
  {
    head = null;
  }
  void enter( Shape a )
  {
    head = new ListNode( a, head );
  }
  double totalArea()
  {
    double total = 0.0;
    for (ListNode p = head; p != null; p = p.next)
      total += p.info.area();
    return total;
  }
}

public static void main(String [] args)
{
  Picture p;
  p.enter( new Triangle(10,10) );
  p.enter( new Square(10) );
  System.out.println("Total area = " + p.totalArea() + '\n');
}

interface Runable
{
  void init();
  void start();
  void stop();
  void destroy();
}

Class RunningCircle
  extends Circle
  implements Runable
{
  void init() { ... }
  ...
}

interface RunableCar
  extends Runable
{	// in addition to the abstract methods of Runable, add the following
  void turnLeft();
  void turnRight();
  void break();
  void accelerate();
}

try
{
  // this statement execute,
  // if an exception is thrown, its caught below
}
catch (SomeException e)
{
  // come here if SomeException is thrown
}
catch (OtherException e)
{
  // come here if OtherException is thrown
}
finally
{
  // always excute this statement no matter how we leave the try block
}

public void openFile()
  throws SomeException, OtherException
{
  throw new SomeException("Oops!");
}

import java.io.*;
class FileIOTest
{
   public static void main(String argv[])
   {
     String pat = "for"; // or whatever you want to find
     String inFile = "input.txt"
     String outFile = "output.txt";  
     String s;
     try {
       BufferedReader br =
        new BufferedReader(new FileReader(inFile));
       PrintWriter pw =
        new PrintWriter(new BufferedWriter(new FileWriter(outFile)));
       while ( (s = br.readLine()) != null )
        if (s.indexOf(pat) > -1)
           pw.println(s);
       br.close();
       pw.close();
     }
     catch (IOException e) {system.out.println(e.toString());}
   }
}