Display a rainbow. - Java 2D Graphics

Java examples for 2D Graphics:Arc

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Description

Display a rainbow.

Demo Code

import javax.swing.JFrame;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;

class DrawRainbow extends JPanel
{
   // define indigo and violet
   private final static Color VIOLET = new Color(128, 0, 128);
   private final static Color INDIGO = new Color(75, 0, 130);
   //from  w  w w .  j a v  a 2 s.com
   // colors to use in the rainbow, starting from the innermost
   // The two white entries result in an empty arc in the center
   private Color[] colors =
      {Color.WHITE, Color.WHITE, VIOLET, INDIGO, Color.BLUE,
       Color.GREEN, Color.YELLOW, Color.ORANGE, Color.RED};
        
   // constructor
   public DrawRainbow()
   {
      setBackground(Color.WHITE); // set the background to white
   } // end DrawRainbow constructor
        
   // draws a rainbow using concentric arcs
   public void paintComponent(Graphics g)
   {
      super.paintComponent(g);
      
      int radius = 20; // radius of an arc
      
      // draw the rainbow near the bottom-center
      int centerX = getWidth() / 2;
      int centerY = getHeight() - 10;

      // draws filled arcs starting with the outermost
      for (int counter = colors.length; counter > 0; counter--)
      {
         // set the color for the current arc
         g.setColor(colors[counter - 1]);
         
         // fill the arc from 0 to 180 degrees
         g.fillArc(centerX - counter * radius,
            centerY - counter * radius, 
            counter * radius * 2, counter * radius * 2, 0, 180);
      } 
   } 
}

public class Main
{
   public static void main(String[] args)
   {
      DrawRainbow panel = new DrawRainbow();      
      JFrame application = new JFrame();
      
      application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      application.add(panel);
      application.setSize(400, 250);
      application.setVisible(true);
   } 
}

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