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Class not found exception

Greenhorn

Posts: 12

posted 6 years ago

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Trying to run an applet using appletviewer and getting this in cmd:

c:\Users\Joshu\Downloads\Snake game\package com.zetcode>appletviewer SnakeGame.html
load: class com.zetcode/Snake.class not found.
java.lang.ClassNotFoundException: com.zetcode.Snake.class
at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:219)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:152)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:634)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:799)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:728)
at sun.applet.AppletPanel.run(AppletPanel.java:378)
at java.lang.Thread.run(Thread.java:748)

This is what is in the directory I'm calling appletviewer from:

Directory of c:\Users\Joshu\Downloads\Snake game\package com.zetcode

18/07/2017 14:21 <DIR> .
18/07/2017 14:21 <DIR> ..
18/07/2017 13:44 187 Board$1.class
18/07/2017 13:44 1,143 Board$TAdapter.class
18/07/2017 13:44 4,654 Board.class
18/07/2017 12:49 5,629 Board.java
18/07/2017 13:44 468 Snake$1.class
18/07/2017 13:44 782 Snake.class
18/07/2017 12:50 683 Snake.java
18/07/2017 14:24 221 SnakeGame.html
8 File(s) 13,767 bytes
2 Dir(s) 435,662,188,544 bytes free

This is the html file:

<!DOCTYPE html>
<html>
<head>
<title>Snake Game</title>
</head>
<body>
<APPLET code="com.zetcode/Snake." width="300" height="180"> Sorry your browser isn't able to run java applets
</APPLET>
</body>
</html>

This is the Snake.java file:

This is the board.java file:

package com.zetcode;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Board extends JPanel implements ActionListener {

private final int B_WIDTH = 300;
    private final int B_HEIGHT = 300;
    private final int DOT_SIZE = 10;
    private final int ALL_DOTS = 900;
    private final int RAND_POS = 29;
    private final int DELAY = 140;

private final int x[] = new int[ALL_DOTS];
    private final int y[] = new int[ALL_DOTS];

private int dots;
    private int apple_x;
    private int apple_y;

private boolean leftDirection = false;
    private boolean rightDirection = true;
    private boolean upDirection = false;
    private boolean downDirection = false;
    private boolean inGame = true;

private Timer timer;
    private Image ball;
    private Image apple;
    private Image head;

public Board() {

addKeyListener(new TAdapter());
        setBackground(Color.black);
        setFocusable(true);

setPreferredSize(new Dimension(B_WIDTH, B_HEIGHT));
        loadImages();
        initGame();
    }

private void loadImages() {

ImageIcon iid = new ImageIcon("dot.png");
        ball = iid.getImage();

ImageIcon iia = new ImageIcon("apple.png");
        apple = iia.getImage();

ImageIcon iih = new ImageIcon("head.png");
        head = iih.getImage();
    }

private void initGame() {

dots = 3;

for (int z = 0; z < dots; z++) {
            x[z] = 50 - z * 10;
            y[z] = 50;
        }

locateApple();

timer = new Timer(DELAY, this);
        timer.start();
    }

@Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);

doDrawing(g);
    }
    
    private void doDrawing(Graphics g) {
        
        if (inGame) {

g.drawImage(apple, apple_x, apple_y, this);

for (int z = 0; z < dots; z++) {
                if (z == 0) {
                    g.drawImage(head, x[z], y[z], this);
                } else {
                    g.drawImage(ball, x[z], y[z], this);
                }
            }

Toolkit.getDefaultToolkit().sync();

} else {

gameOver(g);
        }        
    }

private void gameOver(Graphics g) {
        
        String msg = "Game Over";
        Font small = new Font("Helvetica", Font.BOLD, 14);
        FontMetrics metr = getFontMetrics(small);

g.setColor(Color.white);
        g.setFont(small);
        g.drawString(msg, (B_WIDTH - metr.stringWidth(msg)) / 2, B_HEIGHT / 2);
    }

private void checkApple() {

if ((x[0] == apple_x) && (y[0] == apple_y)) {

dots++;
            locateApple();
        }
    }

private void move() {

for (int z = dots; z > 0; z--) {
            x[z] = x[(z - 1)];
            y[z] = y[(z - 1)];
        }

if (leftDirection) {
            x[0] -= DOT_SIZE;
        }

if (rightDirection) {
            x[0] += DOT_SIZE;
        }

if (upDirection) {
            y[0] -= DOT_SIZE;
        }

if (downDirection) {
            y[0] += DOT_SIZE;
        }
    }

private void checkCollision() {

for (int z = dots; z > 0; z--) {

if ((z > 4) && (x[0] == x[z]) && (y[0] == y[z])) {
                inGame = false;
            }
        }

if (y[0] >= B_HEIGHT) {
            inGame = false;
        }

if (y[0] < 0) {
            inGame = false;
        }

if (x[0] >= B_WIDTH) {
            inGame = false;
        }

if (x[0] < 0) {
            inGame = false;
        }
        
        if(!inGame) {
            timer.stop();
        }
    }

private void locateApple() {

int r = (int) (Math.random() * RAND_POS);
        apple_x = ((r * DOT_SIZE));

r = (int) (Math.random() * RAND_POS);
        apple_y = ((r * DOT_SIZE));
    }

@Override
    public void actionPerformed(ActionEvent e) {

if (inGame) {

checkApple();
            checkCollision();
            move();
        }

repaint();
    }

private class TAdapter extends KeyAdapter {

@Override
        public void keyPressed(KeyEvent e) {

int key = e.getKeyCode();

if ((key == KeyEvent.VK_LEFT) && (!rightDirection)) {
                leftDirection = true;
                upDirection = false;
                downDirection = false;
            }

if ((key == KeyEvent.VK_RIGHT) && (!leftDirection)) {
                rightDirection = true;
                upDirection = false;
                downDirection = false;
            }

if ((key == KeyEvent.VK_UP) && (!downDirection)) {
                upDirection = true;
                rightDirection = false;
                leftDirection = false;
            }

if ((key == KeyEvent.VK_DOWN) && (!upDirection)) {
                downDirection = true;
                rightDirection = false;
                leftDirection = false;
            }
        }
    }
}

Any ideas?

Tony Docherty

Bartender

Posts: 3323

posted 6 years ago

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The problem is your directory structure. It should be:

c:\Users\Joshu\Downloads\Snake game\package\com\zetcode

or probably

c:\Users\Joshu\Downloads\Snake game\com\zetcode

depending on whether you want a directory called 'package' in there or not.

BTW I can't see how you could have compiled the code as is, am I right in thinking you downloaded the class files along with the Java files?

Josh Diamond

Greenhorn

Posts: 12

posted 6 years ago

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Changed the directory structure and still getting this:

C:\Users\Joshu\Downloads\Snake game\com\zetcode>appletviewer SnakeGame.html
load: class com.zetcode/Snake not found.
java.lang.ClassNotFoundException: com.zetcode.Snake
at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:219)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:152)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:634)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:799)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:728)
at sun.applet.AppletPanel.run(AppletPanel.java:378)
at java.lang.Thread.run(Thread.java:748)

Josh Diamond

Greenhorn

Posts: 12

posted 6 years ago

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Tony Docherty wrote:

BTW I can't see how you could have compiled the code as is, am I right in thinking you downloaded the class files along with the Java files?

No I compiled it normally using javac

Tony Docherty

Bartender

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posted 6 years ago

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You need to run the appletviewer from the 'snake game' directory

Josh Diamond

Greenhorn

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posted 6 years ago

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Got this:

C:\Users\Joshu\Downloads\Snake game> appletviewer com/zetcode/SnakeGame.html
load: class com.zetcode/Snake not found.
java.lang.ClassNotFoundException: com.zetcode.Snake
at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:219)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:152)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:634)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:799)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:728)
at sun.applet.AppletPanel.run(AppletPanel.java:378)
at java.lang.Thread.run(Thread.java:748)

Josh Diamond

Greenhorn

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posted 6 years ago

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Is that what you mean by running appletviewer from the SnakeGame directory?

Stephan van Hulst

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Posts: 15124

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posted 6 years ago

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The code attribute of your applet tag should read "com.zetcode.Snake.class".

Norm Radder

Rancher

Posts: 5007

posted 6 years ago

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Why are you using appletviewer and an html file? The posted Snake class is NOT an applet.
Try using the java command instead.

Tony Docherty

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posted 6 years ago

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Well spotted Norm.

Josh Diamond

Greenhorn

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posted 6 years ago

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Thanks for spotting my stupid mistake but when I run it it just shows a black screen which then says GameOver in the middle. Can someone else try running it and see if the same thing happens?

Norm Radder

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posted 6 years ago

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shows a black screen which then says GameOver

What variable(s) and conditions in the program would cause that to happen?

Have you tried debugging the code to see why it does that?

Tony Docherty

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posted 6 years ago

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My guess is you are not actually loading your ball, image and head icons and so nothing is getting displayed and after 'n' seconds the invisible ball goes out of bounds and the game finishes.

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