logo

Object-Oriented Thinking

   

Added on  2019-09-16

5 Pages1704 Words173 Views
 | 
 | 
 | 
LISTING 4.7//******************************************************************** // Splat.java Author: Lewis/Loftus // // Demonstrates the use of graphical objects. //******************************************************************** import javax.swing.*; import java.awt.*; public class Splat { //----------------------------------------------------------------- // Presents a collection of circles. //----------------------------------------------------------------- public static void main(String[] args) { JFrame frame = new JFrame("Splat"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(new SplatPanel()); frame.pack(); frame.setVisible(true); } }
Object-Oriented Thinking_1

Let’s look at another example. The Splat class shown in Listing 4.7 contains a main method that creates and displays the frame for the program. Visually, this program simply draws a few filled circles. The interesting thing about this program is not what it does, but how it does it—each circle drawn in this program is represented by its own object.The main method instantiates a SplatPanel object and adds it to the frame. The SplatPanel classis shown in Listing 4.8. Like the SmilingFacePanel class in the previous example, the SplatPanel class is derived from JPanel. It holds as instance data five Circle objects, which are instantiated in the constructor.LISTING 4.8//******************************************************************** // SplatPanel.java Author: Lewis/Loftus // // Demonstrates the use of graphical objects. //******************************************************************** import javax.swing.*; import java.awt.*; public class SplatPanel extends JPanel { private Circle circle1, circle2, circle3, circle4, circle5; //----------------------------------------------------------------- // Constructor: Creates five Circle objects. //----------------------------------------------------------------- public SplatPanel() { circle1 = new Circle(30, Color.red, 70, 35); circle2 = new Circle(50, Color.green, 30, 20); circle3 = new Circle(100, Color.cyan, 60, 85); circle4 = new Circle(45, Color.yellow, 170, 30); circle5 = new Circle(60, Color.blue, 200, 60); setPreferredSize(new Dimension(300, 200)); setBackground(Color.black); } //----------------------------------------------------------------- // Draws this panel by requesting that each circle draw itself. //----------------------------------------------------------------- public void paintComponent(Graphics page) { super.paintComponent(page); circle1.draw(page); circle2.draw(page); circle3.draw(page);
Object-Oriented Thinking_2

End of preview

Want to access all the pages? Upload your documents or become a member.

Related Documents
Dartboard Applet in Java
|3
|579
|419