几经周折，编译好程序生成.class文件，用java 执行时无出现预期显示，而出现以下文字，求解。
C:\Users\Jacob>java -classpath e:\program\OurFirstProgram
Usage: java [-options] class [args...]
           (to execute a class)
   or  java [-options] -jar jarfile [args...]
           (to execute a jar file)

where options include:
    -client       to select the "client" VM
    -server       to select the "server" VM
    -hotspot      is a synonym for the "client" VM  [depre
                  The default VM is client.

    -cp <class search path of directories and zip/jar file
    -classpath <class search path of directories and zip/j
                  A ; separated list of directories, JAR a
                  and ZIP archives to search for class fil
    -D<name>=<value>
                  set a system property
    -verbose[:class|gc|jni]
                  enable verbose output
    -version      print product version and exit
    -version:<value>
                  require the specified version to run
    -showversion  print product version and continue
    -jre-restrict-search | -jre-no-restrict-search
                  include/exclude user private JREs in the
    -? -help      print this help message
    -X            print help on non-standard options
    -ea[:<packagename>...|:<classname>]
    -enableassertions[:<packagename>...|:<classname>]
                  enable assertions
    -da[:<packagename>...|:<classname>]
    -disableassertions[:<packagename>...|:<classname>]
                  disable assertions
    -esa | -enablesystemassertions
                  enable system assertions
    -dsa | -disablesystemassertions
                  disable system assertions
    -agentlib:<libname>[=<options>]
                  load native agent library <libname>, e.g
                    see also, -agentlib:jdwp=help and -age
    -agentpath:<pathname>[=<options>]
                  load native agent library by full pathna
    -javaagent:<jarpath>[=<options>]
                  load Java programming language agent, se

    -splash:<imagepath>
                  show splash screen with specified image

先看看环境变量有没有问题，然后就是。。。好像命令不是那样执行的吧：
。。。。。。java  E:\My     //运行E下的My.class,具体的楼主自己改下

是命令行不正确

不行,按2楼的输入:java e:\program\OurFirstProgram 后就出现如下提示。

C:\Users\Jacob>java e:\program\OurFirstProgram
Exception in thread "main" java.lang.NoClassDefFoundError: e:\program\OurFirstPr
ogram
Caused by: java.lang.ClassNotFoundException: e:\program\OurFirstProgram
        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)
Could not find the main class: e:\program\OurFirstProgram.  Program will exit.
按教材的解释好像是找不到类，但我在执行前明明用javac编译了并生成了.class文件，为何还执行不了。。。。。。

我的jdk安装在c盘，在执行前，我运行了此参数：path c:\program files\java\jdk1.6\bin   
以下是我按教材里的源码，请各位指教一下我哪里出错了。
public class OurFirstProgram
{
    public static void main(String[] args)
    {
        System.out.println("Kratatoa EAST of Java??");
        }
    }
按书上的例子练习编写了几个程序,结果都和上面一样.
编写后.java和.class文件都齐全，用cmd运行java。

[ 本帖最后由 cocopig 于 2011-1-9 23:31 编辑 ]

原来要先进入保存.CLASS的文件夹在运行。。。。。。。搞了一大堆终于有反应了。