修改Swing窗口风格

String look;

java：
   look = "javax.swing.plaf.metal.MetalLookAndFeel";
Windows:
   look = "com.sun.java.swing.plaf.windows.WindowsLookAndFeel";
Unix:
   look = "com.sun.java.swing.plaf.motif.MotifLookAndFeel"

Mac:
   look = "com.sun.java.swing.plaf.mac.MacLookAndFeel";
GTK:
   look = "com.sun.java.swing.plaf.gtk.GTKLookAndFeel";
当前操作系统风格：
  look=UIManager.getSystemLookAndFeelClassName() ；

设置操作风格：UIManager.setLookAndFeel（look）；