Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

macOS Java help

L

larswik

macrumors 68000
Original poster
Sep 8, 2006
1,552
11
So I finished my 3rd Java class and I decided to work on the homework at home and not in the lab. I typed out the assignment and I am getting 1 error. The public class CompareInts, the CompareInts is causing a problem

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

Code: 
public class [COLOR="Red"]CompareInts[/COLOR] extends Applet implements ActionListener
		{
	Label prompt1;
	TextField input1;
	Label prompt2;
	TextField input2;
	int number1, number2;
	
	public void init()
	{
	prompt1 = new Label ("Enter an Integer: ");
		add (prompt1);
		
		input1 = new TextField(10);
		add (input1);
		
		prompt2 = new Label ("Enter an Integer and press return");
		add (prompt2);
		
		input2 = new TextField (10);
		input2.addActionListener( this);
		add (input2);
	}
	
	public void paint(Graphics g)
	{
		g.drawString("The comparison results are: ", 70, 75);
		
		if (number1 == number2)
			g.drawString(number1 + "==" + number2, 100, 90);
		
		if (number1 != number2)
			g.drawString(number1 + "!=" + number2, 100, 105);
		
		if (number1 < number2)
			g.drawString(number1 + "<" + number2, 100, 120);
		
		if (number1 > number2)
			g.drawString(number1 + ">" + number2, 100, 135);
		
		if (number1 <= number2)
			g.drawString(number1 + "<=" + number2, 100, 150);
		
		if (number1 >= number2)
			g.drawString(number1 + ">=" + number2, 100, 165);
	}
	
	public void actionPerfprmed( ActionEvent e)
	{
		number1 = Integer.parseInt( input1.getText());
		number2 = Integer.parseInt( input2.getText());
		repaint();
	}

}

Now that is just the name of my class so it should not matter what it is, right?
 
I solved part of the problem so far go over the code line by line. I had a typo in the 'public void actionPerformed'. Now it won't let me build it even though I discovered that typo and I get this error. It's my first time using Eclipse, i miss Xcode

Code: 
load: class Comparison.class not found.
java.lang.ClassNotFoundException: Comparison.class
	at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:211)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:144)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:662)
	at sun.applet.AppletPanel.createApplet(AppletPanel.java:807)
	at sun.applet.AppletPanel.runLoader(AppletPanel.java:714)
	at sun.applet.AppletPanel.run(AppletPanel.java:368)
	at java.lang.Thread.run(Thread.java:680)
 
larswik said:
I solved part of the problem so far go over the code line by line. I had a typo in the 'public void actionPerformed'. Now it won't let me build it even though I discovered that typo and I get this error. It's my first time using Eclipse, i miss Xcode

Code: 
load: class Comparison.class not found.
java.lang.ClassNotFoundException: Comparison.class
	at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:211)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:144)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:662)
	at sun.applet.AppletPanel.createApplet(AppletPanel.java:807)
	at sun.applet.AppletPanel.runLoader(AppletPanel.java:714)
	at sun.applet.AppletPanel.run(AppletPanel.java:368)
	at java.lang.Thread.run(Thread.java:680)
Click to expand...

Well you called your class CompareInts and not Comparison, so no wonder the JVM cannot find what you are looking for.
 
larswik said:
I solved part of the problem so far go over the code line by line. I had a typo in the 'public void actionPerformed'. Now it won't let me build it even though I discovered that typo and I get this error. It's my first time using Eclipse, i miss Xcode

Code: 
load: class Comparison.class not found.
java.lang.ClassNotFoundException: Comparison.class
	at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:211)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:144)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
	at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:662)
	at sun.applet.AppletPanel.createApplet(AppletPanel.java:807)
	at sun.applet.AppletPanel.runLoader(AppletPanel.java:714)
	at sun.applet.AppletPanel.run(AppletPanel.java:368)
	at java.lang.Thread.run(Thread.java:680)
Click to expand...

It looks like the run configuration in Eclipse is set up to run an applet called Comparison, and not CompareInts.

Try creating a new run configuration by right-clicking on CompareInts.java in the package explorer, going into Run As, and choosing Java Applet.
 
Thanks Jim that worked! I wonder why it is not working. From what I read the public class CompareInts is like creating a new class in object - C and calling it CompareInts. I don't see why it would not run.

But it is good now, thanks!

-Lars
 
larswik said:
Thanks Jim that worked! I wonder why it is not working. From what I read the public class CompareInts is like creating a new class in object - C and calling it CompareInts. I don't see why it would not run.

But it is good now, thanks!

-Lars
Click to expand...

Well, Java is a bit different than C in that regard. In C you essentially compile all the files into one big file, and as long as one of those files(and only one of those files) has a main method then you can compile into an executable and call that executable whatever you want.

Java does not work like that, you have to specify which class's main you are intending to use, and that name has to match exactly, which is why your code wasn't executing.
 
Just to be very clear, a *.java file can contain 1 public class and other package level classes (or all package level classes) but the name of the *.java file must match exactly the name of that public class (or one of the package level classes if all the classes are package level). For example

FooBar.java can contain

Code: 
public class FooBar {}
class Foo {}
class Bar {}

or

Code: 
class FooBar {}
class Foo {}
class Bar {}

but it can not contain

Code: 
class FooBar {}
class Foo {}
public class Bar {}
 
Last edited by a moderator:
I see that. The TA in the course said that the Mac version of Java using Eclipse might be different then the Windows version very slightly when it comes to writing code. So I thought there might be a difference with me copying the assignment on paper to Eclipse program.

Thanks for the explanation.

-Lars
 
larswik said:
I see that. The TA in the course said that the Mac version of Java using Eclipse might be different then the Windows version very slightly when it comes to writing code. So I thought there might be a difference with me copying the assignment on paper to Eclipse program.

Thanks for the explanation.

-Lars
Click to expand...

On the absolute extreme edges there are some differences, for instance the case of your class file names. I once saw a jar file which, although written in pure Java, was designed only to run on Windows. The programmer ensured that by doing some really spooky things with the .class file names inside the jar. However they are 99.9% the same, esp. at the level you are working at.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back