Problem running Simple Hello world program in Ubuntu

Problem running Simple Hello world program in Ubuntu...

I have installed JDK7... copied it to /usr/lib/jvm/ directory and changed the Java Alternative

And use javac command to compile the program and it created a hello.class file

Code:

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javac hello.java

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it compiled without any error

below is the code

Code:

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

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But when i try to run the prgram using this command

Code:

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java hello

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But i get this following errors

Code:

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Exception in thread "main" java.lang.UnsupportedClassVersionError: Hello : Unsupported major.minor version 51.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
Could not find the main class: Hello.  Program will exit.

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At last line it says Could not find the main class: Hello. Program will exit.

Please help me ,i'm new to Java

Quote:

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UnsupportedClassVersionError: Hello : Unsupported major.minor version 51.0

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It look likes your Java Runtime version(6) is different to your JDK version(7).
What says "java -version" in your terminal? (6?)
You have to change it....

Quote:

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Originally Posted by eRaaaa

It look likes your Java Runtime version(6) is different to your JDK version(7).
What says "java -version" in your terminal? (6?)
You have to change it....

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After executing that command ,i got following text

java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) Client VM (build 19.1-b02, mixed mode, sharing)


Im using JDK 7

Yes, that was what I suspected ->
How do you changed the java alternative?
sudo update-alternatives --config java ?
Do you have selected the java 7 jre?
How To Install Oracle Java 7 (JDK) In Ubuntu ~ Web Upd8: Ubuntu / Linux blog
+ many other sites will give you an installation guide!

Quote:

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Originally Posted by eRaaaa

Yes, that was what I suspected ->
How do you change the java alternative?
sudo update-alternatives --config java ?
Do you have selected the java 7 jre?
How To Install Oracle Java 7 (JDK) In Ubuntu ~ Web Upd8: Ubuntu / Linux blog
+ many other sites will give you a installation guide!

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Thanks a lot .....thank you very much....
i had to change the java alternative,it was set to /usr/lib/jvm/java-6-sun/jre/bin/java
changed it to /usr/lib/jvm/jdk1.7.0/bin/java

so now it works ...thank you :)