Java N00b Help!

[trance]

Exception in thread "main" java.lang.NoSuchMethodError: main

I think it has something to do with java not having the right path? I remembered my professor entering a command to tell java where the folder of the .javas are. Any help?

 

[clamum]

Are you sure your main method signature looks like this?

public static void main(String [] args)

 

[trance]

I'm also getting this error:

'Javac" is not recognized as an internal or external command, operable program or batch file.

 

[clamum]

Are you using some form of Linux? I believe you have to set your path in a config file to point to the Java executables but I don't know a lot about Linux so someone else will have to help ya there.

 

[trance]

I just wrote the Helloworld and it still comes up with that "Javac is not recognized":


public class Hello {

public static void main(String[] args)
{
System.out.println("Hello World!");
}

}

 

[trance]

No, I am using WinXP.

 

[AFB]

http://www.jcreator.com/

It will solve your problem. You normal have to be in the JDK/bin directory to use javac

 

[kimagurealex]

you have to change the enviroment setting in the XP in order to use the javac from anywhere. The Jcreator is a good free ware for Java programming.

Alex

 

[kamper]

But if you still want to do it from the commandline (very useful for learning) you will have to set your system path.

On windows the easiest way is to Rightclick on MyComputer -> Properties -> Advanced -> Environment Variables

Find "Path" in the bottom list, edit it and add the path to your java installation plus "\bin" as amdfanboy points out.

Click all the OKs, restart the command prompt and try to compile again.

The thing that makes me curious though is that you seem to be able to run java.exe but not javac.exe. Did you install java yourself? Are you sure you have the sdk installed and not just the runtime environment?

 

[trance]

yeah I"m installing the JSDK

I told you guys I am a n00b.

 

[MartyMcFly3]

Hey also a noob here.. for class we are supposed to write an expression for the following:

set the value of a to the remainder of b divided by c if b*c is greater than a*c or if y is true. Otherwise, set the value of a to b*c, increment c and set the value of z to false

I have come up with:

If (b*c>a*c) a=b%c
If (y=true) a=b%c
Else

and im stuck with the rest. Im not sure if what I even have is right. The guy sucks at teaching the course so its been a struggle for me.

 

[AFB]

Originally posted by: MartyMcFly3
Hey also a noob here.. for class we are supposed to write an expression for the following:

set the value of a to the remainder of b divided by c if b*c is greater than a*c or if y is true. Otherwise, set the value of a to b*c, increment c and set the value of z to false

I have come up with:

If (b*c>a*c) a=b%c
If (y=true) a=b%c
Else

and im stuck with the rest. Im not sure if what I even have is right. The guy sucks at teaching the course so its been a struggle for me.

Always use brakets even if you don't need the. It is much better style. You can use logical operators ( || , &&, !) to perform multiple boolean checks at the same time.

( (b*c > a*c) || y ) // means b*c is greater than a*c or y is true

 

[amdskip]

I was just helping him on aim amdfanboy, got the same thing as you and I'm gonna help him understand it.

 

[MartyMcFly3]

Thanks for your help guys.

 

[kamper]

Originally posted by: trance
yeah I"m installing the JSDK

I told you guys I am a n00b.

And back to the original post: when you do get javac to work you will see a file called Hello.class in the same folder as your java file. This is the compiled output and will always have the same name as the java file (until you start putting multiple classes in one file but that's another story ). When you say "java Hello" it looks for that class file and tries to run it.

 

[AFB]

Originally posted by: kamper

Originally posted by: trance
yeah I"m installing the JSDK

I told you guys I am a n00b.

And back to the original post: when you do get javac to work you will see a file called Hello.class in the same folder as your java file. This is the compiled output and will always have the same name as the java file (until you start putting multiple classes in one file but that's another story ). When you say "java Hello" it looks for that class file and tries to run it.

It gets even better with anonymous inner classes. Who ever thought of the naming for that should be shot.

 

[kamper]

Anonymous inner classes don't get their own file do they? And what's wrong with the naming?

 

[AFB]

Originally posted by: kamper
Anonymous inner classes don't get their own file do they? And what's wrong with the naming?

They sure do. They get names like Class$1 and things like that.

 

[kamper]

Originally posted by: amdfanboy

Originally posted by: kamper
Anonymous inner classes don't get their own file do they? And what's wrong with the naming?

They sure do. They get names like Class$1 and things like that.

Right you are. So what are your suggestions for the naming?

 

[AFB]

Originally posted by: kamper

Originally posted by: amdfanboy

Originally posted by: kamper
Anonymous inner classes don't get their own file do they? And what's wrong with the naming?

They sure do. They get names like Class$1 and things like that.

Right you are. So what are your suggestions for the naming?

I didn't say I had any better ideas . They probably should have been given the inner class name as their filename. Right now it just looks like a hack (which it is)

 

[kamper]

Anonymous inner classes don't have names, non-anonymous classes do have the class names as part of the filename. I figure it's just the most straightforward way for the compiler and classloaders to communicate which class file should be used when needed. It's not like humans have to deal with them much.

 

[kamper]

Dammit, double post and it wasn't even the forum's fault

 

[AFB]

Originally posted by: kamper
Anonymous inner classes don't have names, non-anonymous classes do have the class names as part of the filename. I figure it's just the most straightforward way for the compiler and classloaders to communicate which class file should be used when needed. It's not like humans have to deal with them much.

I have no idea why I said that. The anonymous kind of gives that way . Yeah, I really can't think of a better way, but I still can rant, can't I ?