1、代码：

     java.awt.Toolkit tk=java.awt.Toolkit.getDefaultToolkit();

      java.awt.Dimension screenSize=tk.getScreenSize();

      int screenWidth=screenSize.width;

             //System.out.println(screenWidth);//1440

      int screenHeight=screenSize.height;

            //System.out.println(screenHeight);//900

 简化：

      Dimension screen=Toolkit.getDefaultToolkit().getScreenSize();

      System.out.println(screen.width);