问题
When I ran a java program I received this error.. Could you please suggest why do we get this error:
Exception in thread "main" java.lang.UnsupportedClassVersionError:
GenerateInvoice (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
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)
回答1:
This class was compiled with a JDK more recent than the one used for execution.
The easiest is to install a more recent JRE on the computer where you execute the program. If you think you installed a recent one, check the JAVA_HOME and PATH environment variables.
Version 49 is java 1.5. That means the class was compiled with (or for) a JDK which is yet old. You probably tried to execute the class with JDK 1.4. You really should use one more recent (1.6 or 1.7, see java version history).
回答2:
Another option is to delete all the classes and rebuild. Having build file is an ideal solution to control whole process like compilation, packaging and deployment. You can also specify source/target versions
回答3:
The code was most likely compiled with a later JDK (without using cross-compilation options) and is being run on an earlier JRE. While upgrading the JRE is one solution, it would be better to use the cross-compilation options to ensure the code will run on whatever JRE is intended as the minimum version for the app.
回答4:
This was a fresh linux Mint xfce machine
I have been battling this for a about a week. I'm trying to learn Java on Netbeans IDE and so naturally I get the combo file straight from Oracle. Which is a package of the JDK and the Netbeans IDE together in a tar file located here.
located http://www.oracle.com/technetwork/java/javase/downloads/index.html file name JDK 8u25 with NetBeans 8.0.1
after installing them (or so I thought) I would make/compile a simple program like "hello world" and that would spit out a jar file that you would be able to run in a terminal. Keep in mind that the program ran in the Netbeans IDE.
I would end up with this error: java.lang.UnsupportedClassVersionError:
Even though I ran the file from oracle website I still had the old version of the Java runtime which was not compatible to run my jar file which was compiled with the new java runtime.
After messing with stuff that was mostly over my head from setting Paths to editing .bashrc with no remedy.
I came across a solution that was easy enough for even me. I have come across something that auto installs java and configures it on your system and it works with the latest 1.8.*
One of the steps is adding a PPA wasn't sure about this at first but seems ok as it has worked for me
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer
domenic@domenic-AO532h ~ $ java -version java version "1.8.0_25" Java(TM) SE Runtime Environment (build 1.8.0_25-b17) Java HotSpot(TM) Server VM (build 25.25-b02, mixed mode)
I think it also configures the browser java as well.
I hope this helps others.
来源：https://stackoverflow.com/questions/12770622/java-lang-unsupportedclassversionerror