Eclipse - 出現Access restriction: The type XXXX is not accessible due to restriction on required library

參考：http://www.digizol.com/2008/09/eclipse-access-restriction-on-library.html
需求：最近承接一個舊系統翻新的案子，由於舊系統使用了 sun.net.ftp.FtpClient 然而被報錯誤：Access restriction: The type FtpClient is not accessible due to restriction on required library C:\Program Files\Java\jre7\lib\rt.jar

1. Eclipse->window->Preferences
2. Java->Compiler->Errors/Warings
3. Deprecated and restricted API->Forbidden reference將原本下拉Error改為Warring

其實這種作法還真是鴕鳥...視而不見...= =