http://blog.naver.com/joniel?Redirect=Log&logNo=40013318755 모르면 배운다.. ㅡ.ㅡ;; javac -d . -classpath . Circle.java -d : Specify where to place generated class files (packge별 directory를 생성하여 class file생성) -classpath : Specify where to find user class files (참조할 class file위치)