Bây giờ bạn đã đào vào những bí mật của các biểu thức, đó là thời gian để tìm hiểu về một loại mới của nhà điều hành. Cho đến nay, bạn đã nhận được một số thực hành với những hoạt động toán học, cho phép bạn xây dựng khác nhau | classes included in the awt package. Table lists the most commonly used drawing methods in the Graphics class. Table Drawing Methods of the Graphics Class. Method Description clearRect Erases a rectangular area of the canvas. copyArea Copies a rectangular area of the canvas to another area. drawArc Draws a hollow arc. drawLine Draws a straight line. drawOval Draws a hollow oval. drawPolygon Draws a hollow polygon. drawRect Draws a hollow rectangle. drawRoundRect Draws a hollow rectangle with rounded corners. drawString Displays a text string. fillArc Draws a filled arc. fillOval Draws a filled oval. fillPolygon Draws a filled polygon. fillRect Draws a filled rectangle. fillRoundRect Draws a filled rectangle with rounded corners. getColor Retrieves the current drawing color. getFont Retrieves the currently used font. getFontMetrics Retrieves information about the current font. setColor Sets the drawing color. setFont Sets the font. To draw a shape in an applet s display area you only need to call the appropriate method and supply the arguments required by the method. These arguments are based on the coordinates at which you want to draw the shape. For example the following code example draws a straight line from coordinate 5 10 to 20 30 5 10 20 30 The g in the preceding code line is the Graphics object passed to the paint method. As you can see the drawLine method takes four arguments which are X Y coordinate pairs that specify the starting and ending points of the line. TIP There may be times when you need to retrieve information about the system s currently set graphical attributes. Java s Graphics class supplies methods like getColor getFont and getFontMetrics to enable you to obtain this information. Example Drawing a Rectangle Most of the shape-drawing methods are as easy to use as the drawLine method is. Suppose that you want to write an applet that draws a filled rounded rectangle inside a hollow rectangle. You d then add calls to the .
