Question

$ pwd
/home/tu/java/testpackage

$ cat Test.java 
package testpackage;

public class Test {
    public static void main(String[] args) {
        System.out.println("hi");
    }
}

$ javac -version
javac 1.7.0_147

$ java -version
java version "1.6.0_23"
OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre11-0ubuntu1.11.10.2)
OpenJDK Client VM (build 20.0-b11, mixed mode, sharing)

$ cd ..
$ javac -cp . testpackage/Test.java

$ java -cp . testpackage.Test

Exception in thread "main"
java.lang.UnsupportedClassVersionError: testpackage/Test :
Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: testpackage.Test. Program will exit.

What could be wrong in my case of this error?

Answer 1

java utility is not a compiler. It is JVM.

You should compile your code first:

javac -cp . testpackage/Test.java

This will produce Test.class file. Now you can run it:

java -cp . testpackage.Test

Pay attention that when you are running the program you do not have to write .class extension.