Write an application that asks the user to input the radius of a circle as a flo

Question

Write an application that asks the user to input
the radius of a circle as a floating-point number and draws the circle, as well as the values of the
circle's diameter, circumference and area. Use the value 3.14159 for pi. [Note: You may also use the
predefined constant Math.PI for the value of pi. This constant is more precise than the value
3.14159. Class Math is declared in the java.lang package, so you need not import it.] Use the following
formulas (r is the radius):
diameter = 2r
circumference = 2pir
area = pi r^2

Explanation / Answer

package test; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.RenderingHints; import java.awt.Shape; import java.awt.geom.AffineTransform; import java.awt.geom.Ellipse2D; import java.awt.image.BufferedImage; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.UIManager; public class SimplePaint02 { private static final int LINE_THICKNESS = 4; private static final int LINE_GAP = 10; private Color lineColor = Color.red; public static void main(String[] args) { new SimplePaint02(); } public SimplePaint02() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception ex) { } JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new BorderLayout()); frame.add(new TestPane()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public class TestPane extends JPanel { @Override public Dimension getPreferredSize() { return new Dimension(100, 100); } @Override public void paintComponent(Graphics g) { int radius = 50; BufferedImage buffer = new BufferedImage(radius, radius, BufferedImage.TYPE_INT_ARGB); Graphics2D g2d = buffer.createGraphics(); g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION,RenderingHints.VALUE_INTERPOLATION_BILINEAR); Ellipse2D circle = new Ellipse2D.Float(0, 0, radius,radius); //Ellipse2D class Shape clip = g2d.getClip(); g2d.setClip(circle); AffineTransform at = g2d.getTransform(); g2d.setTransform(AffineTransform.getRotateInstance(Math.toRadians(45),radius / 2, radius / 2)); int gap = LINE_GAP; g2d.setColor(Color.WHITE); g2d.fill(circle); g2d.setColor(lineColor); //g2d.setStroke(new BasicStroke(LINE_THICKNESS)); for (int index = 0; index < 10; index++) { int x1 = index*gap-(LINE_THICKNESS/2); int y1 = 0; int x2 = index*gap+(LINE_THICKNESS/2); int y2 = radius; int width = x2 - x1; int height = y2 - y1; g2d.fillRect(x1, y1, width, height); //g2d.drawLine(index * gap, 0, index * gap, getRadius()); } g2d.setTransform(at); g2d.setClip(clip); g2d.dispose(); g.drawImage(buffer, 0, 0, this); } }

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