UnsupportedClassVersionError

[Mg Oo]

Dear Java masters

How to escape such error? I face when I run files in other computers (eg.friends', lab's)

  
C:\Documents and Settings\user\Desktop\g>java -jar sm.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError: net/mmhackers
/SendMail (Unsupported major.minor version 49.0)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(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)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
  

[Ulf Dittmer]

This error occurs if the classes were compiled with a JDK that is newer than the one you're using to run them. Version 49.0 is the one generated by Java 1.5, so you're probably trying to run it with a Java 1.4 JVM.

Try compiling your code with the "-source 1.4 -target 1.4" options. This will only work if you use no Java 5-specific code, of course. If you do, upgrade the JVM on the other machine to Java 5.