What is the best way to start creating java programs?

Energize · 26 Mar 2007 at 18:25

Everytime I try to use an ide I get errors like "cannot resolve symbol" "package system not setup" or something like that and I'm only trying to compile the hello world app! When I try to compile a notepad file I always get "javac is not a recognised command" even though I have set the environmental variables, I don't want to have to keep typing in the directory everytime I want to compile something either.

So can someone please tell me how to create java applications without having to setup loads of complicated things? It's bad enough having to install the sdk without settings up classes or whatever they are called. With C++ I just downloaded the devc++ ide and I could just go "new"---->"file" and start coding and compiling straight away. Is there any program that will allow me to do this for java?

manic_man · 26 Mar 2007 at 18:39

Eclipse might be a good way to start, or the Sun Netbeans IDE. Others exist such as JBuilder but a) they arnt free and b) JBuilder is terrible

if "javac" isnt working at the command line than your environment variables arn't set up correctly!

Energize · 26 Mar 2007 at 18:54

manic_man said:
Eclipse might be a good way to start, or the Sun Netbeans IDE. Others exist such as JBuilder but a) they arnt free and b) JBuilder is terrible

I get those errors I mentioned when I use eclipse. Why can't java just be like c++ where it just works without setting anything up? It seems like java is actually more complicated than c++.

Even my instructor can't figure out why it isn't working!

manic_man · 26 Mar 2007 at 19:02

java is a bit more complicated than C++ in concept

its running on a virtual machine within a "real" machine rather than just being directly compiled to base level machine specific code, your code is then interpreted on the fly by the JVM, so really things are a tad more difficult.

Once your sorted though it gets much easier than it seems when you first start.

I have to say, when i installed the latest Java SDK on my Vista system it just set up all my sys vars etc for me!

Heres a reasonabky good guide though if things still arnt working:

http://www.cs.ucsb.edu/~teliot/Path_and_Classpath.htm

Also ,try netbeans, a lot find it a bit more "user friendly" to begin with althugh eclipse is more powerful and far faster overall.

Una · 26 Mar 2007 at 19:07

You can just compile programs using javac Classname.java then execute them using java Classname. You just have to make sure the right enviromental variables are setup correctly/classpath is correct. In linux if you install sunjava-sdk it automatically configures this for you (not sure about the windows installer).

toString · 26 Mar 2007 at 19:15

We used this at uni in the first year:
http://drjava.org/
Nothing fancy. Just gets right to it. Things like Eclipse are great, but I remember when I tried to use it in the first year I spent ages trying to get it to work.

Energize · 26 Mar 2007 at 19:30

Ok I've compiled the file using javac finally, but not when I type java to try to run it, it fails spectaculary again.

toString · 26 Mar 2007 at 19:38

Show us your code

Edit: try java Test

Class names are always in capitals.

e.g.

Code:

C:\>java HelloWorld.class
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld/class

C:\>java HelloWorld
Hello World!

Energize · 26 Mar 2007 at 19:39

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

toString · 26 Mar 2007 at 19:41

Ahh well you have to use the name of the class, test isn't the name.

It's the correct standard to use the name of the file as the name of the class

i.e.
HelloWorldApp.java
would contain a class called HelloWorldApp..

java HelloWorldApp
should do it

Energize · 26 Mar 2007 at 19:57

I get the same error.

toString · 26 Mar 2007 at 20:12

There must be something very wrong with your setup then

I just tried it as you had it...

test.java:

Code:

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

Code:

C:\>javac test.java

C:\>java test
Exception in thread "main" java.lang.NoClassDefFoundError: test

C:\>java HelloWorldApp
Hello World!

C:\>

NathanE · 26 Mar 2007 at 20:14

Compiling via the command line is not the best way to start creating Java programs

You really should install an IDE, such as NetBeans or Eclipse

Una · 26 Mar 2007 at 20:15

Whats the error?

Energize · 26 Mar 2007 at 20:19

NathanE said:
Compiling via the command line is not the best way to starting creating Java programs

You really should install an IDE, such as NetBeans or Eclipse

I said I already tried that and the errors I get with them, "cannot resolve symbol" and "package system not setup". I've been told though that I should start with the command line because it's good to know how to use it.

Una said:
Whats the error?

I already posted it.

Una · 26 Mar 2007 at 20:20

Energize said:
I said I already tried that and the errors I get with them. I've been told though that I should start with the command line because it's good to know how to use it.

It is good to start with the command line and a syntax hightlight text editor such as VIM. No need to jump straight into an IDE when your learning the basics.

Una · 26 Mar 2007 at 20:25

Try java -cp . Test from the same directory as your program. If that works you got a problem with your CLASSPATH enviromental variable, check that.

Energize · 26 Mar 2007 at 20:29

when I try -cp it says

"usage: java [-options] class [args...] <to execute a class>"

Una · 26 Mar 2007 at 20:32

alex@xor:~$ java -cp . Test
Hello World.

Assuming you got a Test.class in the current directory.

Energize · 26 Mar 2007 at 20:40

Una said:
java -cp . Test

Omg it worked, it's a miracle!