Nicole Gruber

Thanks Steve!!! My program works now!
and also thanks for the tips ;) I'm really grateful!

Hello,
I have this assignment where I am supposed to create a panel with four buttons. If you click one of them, music should begin and loop continuosly, if you click it once more, the music should stop playing. Unfortunatley, I can't manage to do that (stop the music from playing)..
I have two classes: One is called PlayClip(extends Thread) and the other one SimpleClipPlayer(extends JFrame implements ActionListener).
The first class contains also the method run() :
public void run(){ clip.loop(Clip.LOOP_CONTINUOUSLY); }
In the second class are the four buttons and also the method ActionPerformed():
public void actionPerformed(ActionEvent e) { if(e.getSource() == loop0) { PlayClip clip1 = new PlayClip("http://freewavesamples.com/files/Alesis-Fusion-Bass-Loop.wav"); if(this.isRunning == true) { //Sounddatei will be stopped clip1.interrupt(); this.isRunning = false; loop0.setBackground(null); } else { clip1.start(); //start Thread this.isRunning = true; loop0.setBackground(new Color(225,225,0)); } }

I can't use the stop() method because it's deprecated and interrupt() doesn't seem to work. I also tried to use a flag and I've put the method clip.loop(Clip.LOOP_CONTINUOUSLY); in a while-loop, put that doesn't seem to work either..

Can someone help me?

What works: the first time when the user clicks somewhere on the panel, that point is added in the Model-class, which notifices the Observer(View-class) [I omitted to write in the code this.setChanged(); this.notifyObservers();
]
and finally the point is being drew through the paint() Method .
the Problem is that once you click twice on the Panel, the second point doesn't appear anymore...

I have this asignment to create a Java SWING application, which uses the Java2D functionality. The user should be able to draw points on the panel and by pushing the Create Polygon button to unite the points into a polygon. I'm not able to create the Points and I am also confused by the MVC Pattern, wich we are obliged to use! Can someone help me???

import java.awt.*; import java.util.Observable; public class Model extends Observable { private int npoints; private Entry<Point> head; private Entry<Point> tail; public Model() { this.head = null; this.tail = null; this.npoints = 0; } public void add(Point p) { Entry<Point> newLast = new Entry<Point>(p, null, this.tail); if(this.npoints == 0) { this.head = newLast; } else { this.tail.setNext(newLast); } this.tail = newLast; this.npoints++; } public void clear() { this.head = null; this.tail = null; this.npoints = 0; } public Entry<Point> entry(int index) { if(index < 0 || index >= this.npoints) { throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + this.npoints); } Entry<Point> currentPoint = this.head; while(index > 0) { currentPoint = currentPoint.getNext(); index--; } return currentPoint; } public Point get(int index) { return entry(index).getElement(); } public boolean isEmpty() { return this.npoints == 0; } public int size() { return this.npoints; } public Point remove(int index) { Entry<Point> entry = entry(index); if(index == 0) { this.head = entry.getNext(); } else { entry.getPrevious().setNext(entry.getNext()); } if(index == this.npoints - 1) { this.tail = entry.getPrevious(); } else { entry.getNext().setPrevious(entry.getPrevious()); } this.npoints--; return entry.getElement(); } public void set(int index, Point element) { Entry<Point> entry = entry(index); Point oldElement = entry.getElement(); entry.setElement(element); } public Point[] toArray() { Point[] points = new Point[this.npoints]; for(int i = 0; i < this.npoints; i++) { points[i] = this.get(i); } return points; } public int[] xpoints() { int[] xpoints = new int[this.npoints]; for(int i = 0; i < this.npoints; i++) { xpoints[i] = this.get(i).x; } return xpoints; } public int[] ypoints() { int[] ypoints = new int[this.npoints]; for(int i = 0; i < this.npoints; i++) { ypoints[i] = this.get(i).y; } return ypoints; } private static class Entry<Point> { private Point point; private Entry<Point> next; private Entry<Point> previous; public Entry(Point o, Entry<Point> next, Entry<Point> previous) { this.point = o; this.next = next; this.previous = previous; } public Point getElement() { return this.point; } public void setElement(Point element) { this.point = element; } public Entry<Point> getNext() { return this.next; } public void setNext(Entry<Point> element) { this.next = next; } public Entry<Point> getPrevious() { return this.previous; } public void setPrevious(Entry<Point> element) { this.previous = previous; } } }

import java.awt.*; import java.util.Observable; import java.util.Observer; import javax.swing.*; public class View extends JFrame implements Observer { JButton btn1 = new JButton("Create Polygon"); JButton btn2 = new JButton("Choose Color"); JPanel pnl = new JPanel(new FlowLayout()); MyDrawPanel drawPanel = new MyDrawPanel(); public View(Model model) { super("Java2D"); this.setDefaultCloseOperation(EXIT_ON_CLOSE); this.setSize(600,350); this.getContentPane().add(BorderLayout.CENTER, drawPanel); pnl.add(btn1); pnl.add(btn2); this.getContentPane().add(BorderLayout.SOUTH, pnl); Controller c = new Controller(model, drawPanel); btn1.addActionListener(c); btn2.addActionListener(c); drawPanel.addMouseListener(c); this.setVisible(true); } public static void main(String[] args) { Model m = new Model(); View view = new View(m); } @Override public void update(Observable o, Object arg) { Model model = (Model) o; drawPanel.setModel(model); } }

import java.awt.Polygon; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; public class Controller implements MouseListener, ChangeListener, ActionListener{ private Model m; private MyDrawPanel pnl; public Controller(Model m, MyDrawPanel pnl){ this.m = m; this.pnl = pnl; } @Override public void mouseClicked(MouseEvent e) { m.add(e.getPoint()); pnl.repaint(); } @Override public void mouseEntered(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mouseExited(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mousePressed(MouseEvent e) { // TODO Auto-generated method stub } @Override public void mouseReleased(MouseEvent e) { // TODO Auto-generated method stub } @Override public void actionPerformed(ActionEvent e) { Polygon p = new Polygon(); pnl.draw(p); } }


import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import java.awt.geom.Point2D; import java.awt.geom.Rectangle2D; import java.util.Observable; import java.util.Observer; import javax.swing.*; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; class MyDrawPanel extends JPanel { private Model m = new Model(); public void setModel(Model n) { this.m = n; } public void paint(Graphics g){ Graphics2D g2 = (Graphics2D) g; //fuellt das Panel mit Schwarz g2.fillRect(0, 0, this.getWidth(), this.getHeight()); g2.setPaint(Color.WHITE); for(int i = 0; i < m.size(); i++) { if(m.get(i) != null) { g2.fill(getControlPoint(m.get(i))); } } } protected Shape getControlPoint(Point2D p) { // Create a small square around the given point. int side = 4; return new Rectangle2D.Double( p.getX() - side / 2, p.getY() - side / 2, side, side); } public void draw(Polygon p) { if(!(m.isEmpty())){ p = new Polygon(m.xpoints(), m.ypoints(), m.size()); } } }

thanks for your time!
I think I mainly understood ;)

Can someone please explain to me how the Hoare-Calculus works??? Take this exercise for example:
// precondition: 0 <= n i = 0; x = 1; while(i < n) { i = i + 1; x = i * x; } // postcondition: x == n!
n, i , x are int and the notation n! = factorial

yes, you were right. The method double getElement(int index); was missing.
Thanks Rob

Now I think I understood all my faults, thank to all of you who helped!!!

But I can't write v.dimension[n] because I have no dimension variable in the interface Vector... ( and I am not alowed to change the interface Vector.java)

P.S. I also changed the field dimension to int[].

well, i am not suposed to use java.util.Vector.
I have to add up two vectors in the method public Vector plus(Vector v). i know i shouldn't have written return v, but another Vector, for example Vector sum. I just don't know how to do it.. In order to add up two vectors you need to add up each number from the ArrayList. In my example the answer would be a vector: {1+1, 2+2, 3+3}. Now, I don't know how to write that, espacially what to return.
The same problem is at public Vector times(double skalar), where I need to multiply the Vector with a number...
I am a beginner so that all is very difficult for me to understand...

I already have an interface Vector.java and i must create a ReellerVector.java that implements Vektor.java.

public interface Vector { int getDimension(); Vector plus(Vector v); Vector times(double skalar); String to String(); }
ReellerVector.java looks like this:

public class ReellerVector implements Vector { private double[] dimension; public ReellerVector(double[] dimension) { this.dimension = dimension; } public int getDimension() { return dimension.length; } public Vector plus(Vector v) { for(int n = 0; n < dimension.length; n++) { dimension[n] = this.dimension[n] + dimension[n]; } return v; } public Vector times(double skalar) { ReellerVector y = new ReellerVector(dimension); for(int n = 0; n < dimension.length; n++) { dimension[n] = skalar * dimension[n]; } return y; } }

the class Test contains the main Method:

public class Test { public static void main(String[] args) { final double[] N = {1,2,3}; ReellerVector v1 = new ReellerVector(N); ReellerVector v = new ReellerVector(N); System.out.println("v1:" + v1.getDimension()); System.out.println("v1:" + v1.plus(v)); System.out.println("v1:" + v1.times(3)); System.out.println("v1:" + v1.toString()); } }

Of course, it's not right how I wrote ReellerVector.java and therefore I get this Output:
v1: 3
v1: 2.0
v1: Vector: [D@42e816.
v1: Vector: [D@42e816.
v1: Vector: [D@42e816.

Can someone help me ???