不论我运行那个程序都有如下的错误： Exception in thread "main" java.lang.NoClassDefFoundError=con\sun\tools\javac\main 我的系统是XP，查资料说是CLASSPATH的设置有问题，资料上说是在CLASSPATH设置的是CLASS文件的路径。如果用JAVADOC时，错误只是把上面的JAVAC改成了JAVADOC但是，该错误是在JAVAC的时候就出现了啊，如果说缺少CLASS，可我的程序是原题啊。按哩来说是在JAVA的时候才该有的啊，可 我怎么也修改不好 高手救我

[QUOTE] ErrorExplanation Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldAppIf you receive this error, java cannot find your bytecode file,HelloWorldApp.class.One of the places java tries to find your bytecode file isyour current directory. So, if your bytecode file is in C:\java,you should change your current directory to that. To change your directory,type the following command at the prompt and press Enter:

cd c:\java

The prompt should change to C:\java>. If you enter dirat the prompt, you should see your .java and .class files.Now enter java HelloWorldApp again.If you still have problems, you might have to change your CLASSPATHvariable. To see if this is necessary, try "clobbering" the classpath withthe following command:

set CLASSPATH=

Now enter java HelloWorldApp again. If the program works now,you'll have to change your CLASSPATH variable. For more information, consultthe section 5. Update the PATH variable in the installation instructions. [/QUOTE] 下面那个网页你也可以看一下 http://java.sun.com/docs/books/tutorial/getStarted/cupojava/win32.html