java cannot find symbol error

I have a simple file system, in which all the files being used by the main program are in the same folder. The main program is also in the same system. 开发者_JS百科It was actually a jar file by my friend and then I unzipped it using winrar, the class files are running well, but only when i amended something and tried to compile the program i am getting this error of cannot find symbol for one of the class being used, and its right there in the same folder. How can i resolve this please?

Thanks in advance

You have to place your source files into appropriate subfolders. The name of the folder corresponds to your package name, in this case next.

next/Pretty.java
next/Tree.java
...

Then you can compile using command

javac next/*.java

from the base directory.