初学java怎么会出现线程错误啊，帮忙分析下原因啊
程序如下：
程序代码：public class TestJava
{
public static void main(String args[]){
int num = 10;
num = 30;
System.out.println("num的内容是:"+num);
System.out.println("num*num:"+num*num);
}
}
运行的情况：
C:\Documents and Settings\Administrator>f:
F:\>javac TestJava.java
F:\>java TestJava
Exception in thread "main" java.lang.UnsupportedClassVersionError: TestJava (Uns
upported major.minor version 50.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at (Unknown Source)
at (Unknown Source)
at (Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at (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)
各位帮忙分析下啊，这到底是为什么啊？谢谢了啊！
