From man javac on my system:
-d directory
Sets the destination directory for class files. The destination directory must already exist; javac will not create the destination directory. If a class is part of a package, javac puts the class file in a subdirectory reflecting the package name, creating directories as needed. For example, if you specify -d /home/myclasses and the class is called com.mypackage.MyClass, then the class file is called /home/myclasses/com/mypackage/MyClass.class. If -d is not specified, javac puts the class file in the same directory as the source file. Note: The directory specified by -d is not automatically added to your user class path.
Hope that helps.
