Failing miserably at learning Java!

[ThesaurusRex84]

Well, apparently I can't even get a simple HelloWorld program right.

Following this tutorial (with the sole exception of me using Java 7 instead of Java 2, as this was written in 2000), I did the following:

- Open up Notepad.

- Type this in:

public class MyProgram {

  public static void main(String[] args) {
    System.out.println(
      "Eureka, I can put Java on my resume.");
  }
}

- Saved as MyProgram.java

- Opened up Command Prompt, typing javac MyProgram.java to compile it.


Compiling was successful (apparently), as it created a .class file. However, when I typed 'java MyProgram', I got this:

C:\Users\Jonathan\javastuff>java MyProgram
Exception in thread "main" java.lang.UnsupportedClassVersionError: MyProgram :
Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknow n Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: MyProgram. Program will exit.

There are no troubleshooting paragraphs that address this issue, what on earth did I do wrong?

[pbrockway2]

The version number message refers to the fact that you are compiling the code with a newer version of Java than the one you are trying to run it with. The runtime doesn't understand the .class files created by the compiler.

Check the version of the JRE (Java Runtime Environment) to are using. In the Control Panel it will be listed under Programs. Or you can enter the command

java -version

If it is not Java7, download and install the most recent JRE.

[DarrylBurke]

Please go through the Forum Rules -- particularly the third paragraph.

db

[ThesaurusRex84]

1.6.0_31. I coulda sworn it was up to date.


I just installed the Java 7 runtime environment now, but it still said I'm running 1.6.

Please go through the Forum Rules -- particularly the third paragraph.

db

Sorry about that, Darryl. I also should have known that something like this would have been posted before.

[awinston]

Sorry about that, Darryl. I also should have known that something like this would have been posted before.

I think he was actually referring to the the fact that your title doesn't accurately reflect the topic of this thread.

[pbrockway2]

I just installed the Java 7 runtime environment now, but it still said I'm running 1.6.

Make sure the bin directory (folder) of the Java 7 runtime is on your system's path. (an not the older one). Or - more easily - use the control panel to uninstall 1.6.0_31 then reinstall 7.

(In general there's no reason why you shouldn't have multiple versions installed. But while you're still getting used to the language it is probably easiest to have just one.)

[ThesaurusRex84]

Thank you, Brock. This solved my problem!

[pbrockway2]

You're welcome. Good luck with the rest of the Tutorial!