java登陆窗口设计源代码工程文件，用java建立一个类似于qq的登陆窗口，输入用户名密码登陆系统。用于学习java的图形界面设计与多窗口切换设计。-java the landing window design source code project file used the java to establish a similar qq login window, enter your user name and password login system. Graphical interfa