线程“ main”java.lang 中的异常

可能的复制品:
不支持的主要。次要版本51.0

我安装了 JDK7，一个简单的 hello word 程序得到了编译，但是当我运行这个程序时，我得到了以下异常。

Exception in thread "main" java.lang.UnsupportedClassVersionError: a (Unsupported major.minor version 51.0)
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)

我在命令提示符下检查了 java -version，它显示 Java 版本1.4.2 _ 03，但是当我试图从 Java.com 安装新的 Java 版本时，它说我已经推荐了 Java7版本。

323476 次浏览
小开

Sounds like you need to change the path to your java executable to match the newest version. Basically, installing the latest Java does not necessarily mean your machine is configured to use the latest version. You didn't mention any platform details, so that's all I can say.

小开
最佳答案

Copy the contents of the PATH settings to a notepad and check if the location for the 1.4.2 comes before that of the 7. If so, remove the path to 1.4.2 in the PATH setting and save it.

After saving and applying "Environment Variables" close and reopen the cmd line. In XP the path does no get reflected in already running programs.

小开

Try sudo update-alternatives --config java from the command line to set the version of the JRE you want to use. This should fix it.

小开

Assuming you are using Eclipse, on a MAC you can:

  1. Launch Eclipse.app
  2. Choose Eclipse -> Preferences
  3. Choose Java -> Installed JREs
  4. Click the Add... button
  5. Choose MacOS X VM as the JRE type. Press Next.
  6. In the "JRE Home:" field, type /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home
  7. You should see the system libraries in the list titled "JRE system libraries:"
  8. Give the JRE a name. The recommended name is JDK 1.7. Click Finish.
  9. Check the checkbox next to the JRE entry you just created. This will cause Eclipse to use it as the default JRE for all new Java projects. Click OK.
  10. Now, create a new project. For this verification, from the menu, select File -> New -> Java Project.
  11. In the dialog that appears, enter a new name for your project. For this verification, type Test17Project
  12. In the JRE section of the dialog, select Use default JRE (currently JDK 1.7)
  13. Click Finish.

Hope this helps

小开

I had this problem, after installing jdk7 next to Java 6. The binaries were correctly updated using update-alternatives --config java to jdk7, but the $JAVA_HOME environment variable still pointed to the old directory of Java 6.


提交答案