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Installing JDK

 
Joel Handloff
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ok, I'm obviously not very bright...
I've installed the JDK, and I can javac my code.
when I try to run it, I get a NoClassDefFoundError.
I'm assuming that this is some sort of path issue, but wouldn't that prevent me from compiling it in the first place?
code below

public class MyFirstApp {
public static void main (String[] args) {
System.out.println("I Rule!");
}
}
 
Keith Lynn
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What was the exact command that you used to interpret it? Rememember that Java is case-sensitive.

Try this

java -cp . MyFirstApp
 
Joel Handloff
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That gets me:
Exception in thread "main" java.lang.UnsupportedClassVersionError: MyFirstApp (U
nsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
3)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
 
Jesper de Jong
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Welcome to JavaRanch, and welcome to Java!

You have to make sure that you do not have the CLASSPATH environment variable set, or add "." (the current directory) to your classpath.

Read the JDK installation instructions, where setting the classpath is explained, or see the Hello World Tutorial on Sun's website, which explains what you should do if you get this error.
 
Jesper de Jong
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java.lang.UnsupportedClassVersionError: MyFirstApp (Unsupported major.minor version 49.0)

This means that you compiled your source code with Java 1.5, but you are running it with an older version.

Make sure that you have only one version of Java installed on your computer, or make sure that the Java 1.5 binaries are found first in your PATH.
 
Keith Lynn
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It appears that your java refers to an older version of the JDK. This is probably because your PATH does not contain the correct bin directory. What version of the JDK did you install?
 
Joel Handloff
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ok, yes, I probably do have two versions installed on my machine.
I don't think I can resolve that without getting in trouble here at work.
Thanks for you time!!
 
Keith Lynn
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Actually, you can temporarily set your PATH in your working directory so that you use the correct JDK.
 
Keith Lynn
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Another alternative is to use the absolute path of your Java installation.
 
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