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

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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.