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