# teaching machines

## CS 1: Lecture 23 – Loops, Part 5

Dear students,

• Write a program to produce an animated GIF of a bouncing ball.
• Write a program to automatically intersect two words. Like this:
 a
u
t
pumpkin
m
n
• Write a program to play Linesweeper, which is like Minesweeper, but in one dimension.
• Write a program to find all alliterative sequences in a text file. For our purposes, an alliterative sequence is composed of words that all begin with the same letter, as in “Sally said you better buy bananas.”

Here’s your TODO list to complete before we meet again:

• Do not use Graphics or Graphics2D in your homework 4 solutions.
• On a quarter sheet, write method bingo that prints a 5×5 Bingo board. The B column contains random numbers in 1 through 15. The I column 16 through 30… The O column 61 through 75. Allow repeats.

See you next class!

Sincerely,

P.S. It’s time for a haiku!

i went on and on
not knowing y exactly
until i met u

P.P.S. Here’s the code we wrote together in class…

#### Alliterative.java

package lecture1101;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Alliterative {
public static void main(String[] args) throws FileNotFoundException {
File file = new File("/Users/johnch/Desktop/wisconsin.txt");
Scanner in = new Scanner(file);

String run = "";
while (in.hasNext()) {
String current = in.next();

if (run.startsWith("" + current.charAt(0))) {
run += " " + current;
} else {
if (run.contains(" ")) {
System.out.println(run);
}
run = current;
}

}

in.close();
}
}


#### Linesweeper.java

package lecture1101;

import java.util.Random;
import java.util.Scanner;

public class Linesweeper {
public static void main(String[] args) {
String uncovered = getBoard();
String covered = "----------";

Scanner in = new Scanner(System.in);

prompt(covered);
while (in.hasNextInt()) {
int i = in.nextInt();
covered = uncover(covered, uncovered, i);
prompt(covered);
}
}

private static String uncover(String covered,
String uncovered,
int i) {
String newCovered = covered.substring(0, i) +
uncovered.charAt(i) +
covered.substring(i + 1);
return newCovered;
}

private static void prompt(String board) {
System.out.println("0123456789");
System.out.println(board);
System.out.print("Where? ");
}

public static String getBoard() {
String s = "";
Random g = new Random();
for (int i = 0; i < 10; ++i) {
if (g.nextInt(100) < 30) {
s += "*";
} else {
s += ".";
}
}
return s;
}
}


#### GifSequenceWriter.java

package lecture1101;
//  GifSequenceWriter.java

//
//  Created by Elliot Kroo on 2009-04-25.
//
// http://creativecommons.org/licenses/by/3.0/ or send a letter to Creative
// Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

import javax.imageio.*;
import javax.imageio.stream.*;
import java.awt.image.*;
import java.io.*;
import java.util.Iterator;

public class GifSequenceWriter {
protected ImageWriter gifWriter;
protected ImageWriteParam imageWriteParam;
protected ImageOutputStream outputStream;

/**
* Creates a new GifSequenceWriter
*
* @param outputStream
*          the ImageOutputStream to be written to
* @param imageType
*          one of the imageTypes specified in BufferedImage
* @param timeBetweenFramesMS
*          the time between frames in miliseconds
* @param loopContinuously
*          wether the gif should loop repeatedly
* @throws IIOException
*           if no gif ImageWriters are found
*
* @author Elliot Kroo (elliot[at]kroo[dot]net)
*/
public GifSequenceWriter(File outFile,
int timeBetweenFramesMS,
boolean loopContinuously) {
try {
// my method to create a writer
gifWriter = getWriter();
imageWriteParam = gifWriter.getDefaultWriteParam();
ImageTypeSpecifier imageTypeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);

graphicsControlExtensionNode.setAttribute("disposalMethod", "none");
graphicsControlExtensionNode.setAttribute("userInputFlag", "FALSE");
graphicsControlExtensionNode.setAttribute("transparentColorFlag", "FALSE");
graphicsControlExtensionNode.setAttribute("delayTime", Integer.toString(timeBetweenFramesMS / 10));
graphicsControlExtensionNode.setAttribute("transparentColorIndex", "0");

child.setAttribute("applicationID", "NETSCAPE");
child.setAttribute("authenticationCode", "2.0");

int loop = loopContinuously ? 0 : 1;

child.setUserObject(new byte[] { 0x1, (byte) (loop & 0xFF), (byte) ((loop >> 8) & 0xFF)
});
appEntensionsNode.appendChild(child);

outputStream = new FileImageOutputStream(outFile);
gifWriter.setOutput(outputStream);
gifWriter.prepareWriteSequence(null);
} catch (IOException e) {
throw new RuntimeException(e);
}
}

public void appendFrame(BufferedImage img) {
try {
} catch (IOException e) {
throw new RuntimeException(e);
}
}

/**
* Close this GifSequenceWriter object. This does not close the underlying
* stream, just finishes off the GIF.
*/
public void close() {
try {
gifWriter.endWriteSequence();
outputStream.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}

/**
* Returns the first available GIF ImageWriter using
* ImageIO.getImageWritersBySuffix("gif").
*
* @return a GIF ImageWriter object
* @throws IIOException
*           if no GIF image writers are returned
*/
private static ImageWriter getWriter() throws IIOException {
try {
Iterator<ImageWriter> iter = ImageIO.getImageWritersBySuffix("gif");
if (!iter.hasNext()) {
throw new IIOException("No GIF Image Writers Exist");
} else {
return iter.next();
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}

/**
* Returns an existing child node, or creates and returns a new child node (if
* the requested node does not exist).
*
* @param rootNode
*          the <tt>IIOMetadataNode</tt> to search for the child node.
* @param nodeName
*          the name of the child node.
*
* @return the child node, if found or a new node created with the given name.
*/
String nodeName) {
int nNodes = rootNode.getLength();
for (int i = 0; i < nNodes; i++) {
if (rootNode.item(i).getNodeName().compareToIgnoreCase(nodeName) == 0) {
}
}
rootNode.appendChild(node);
return node;
}
}


#### BouncingBall.java

package lecture1101;

import java.awt.Color;
import java.awt.Desktop;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URI;

public class BouncingBall {
public static void main(String[] args) throws IOException {
GifSequenceWriter out = new GifSequenceWriter(new File("/Users/johnch/Desktop/foo.gif"), 16, true);

BufferedImage image = new BufferedImage(700, 400, BufferedImage.TYPE_INT_RGB);
Graphics2D g = image.createGraphics();

double x = 0;
double y = 52;
double xVelocity = 3;
double yVelocity = 7;
double gravity = 9.8;

for (int t = 0; t < 400; ++t) {

if (y + 20 >= image.getHeight()) {
yVelocity *= -0.8;
}

g.setColor(Color.WHITE);
g.fillRect(0, 0, image.getWidth(), image.getHeight());

g.setColor(Color.BLUE);
g.fillOval((int) x, (int) y, 20, 20);

x += xVelocity;
y += yVelocity;
yVelocity += gravity;

out.appendFrame(image);
}

out.close();

Desktop desktop = Desktop.getDesktop();
desktop.browse(URI.create("file:///Users/johnch/Desktop/foo.gif"));
}
}


#### Intersection.java

package lecture1101;

import java.awt.Point;

public class Intersection {
public static void main(String[] args) {
String s1 = "dinosaur";
String s2 = "aardvark";

// i1, i2 = find intersection point
Point p = getIntersection(s1, s2);

// print some stuff
for (int i = 0; i < p.x; ++i) {
System.out.printf("%" + (p.y + 1) + "c%n", s1.charAt(i));
}

System.out.println(s2);

for (int i = p.x + 1; i < s1.length(); ++i) {
System.out.printf("%" + (p.y + 1) + "c%n", s1.charAt(i));
}
}

private static Point getIntersection(String s1,
String s2) {
for (int i1 = 0; i1 < s1.length(); ++i1) {
// s1.charAt(i1)
for (int i2 = 0; i2 < s2.length(); ++i2) {
// s2.charAt(i2)
if (s1.charAt(i1) == s2.charAt(i2)) {
return new Point(i1, i2);
}
}
}
return null;
}
}