Answers for "java draw a function"

how to draw in java

package com.javacodegeeks.snippets.desktop;
 
import java.awt.Component;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Polygon;
 
public class DrawShapesExample {
 
  public static void main(String[] args) {
 
        // Create a frame

        Frame frame = new Frame();

        // Add a component with a custom paint method

        frame.add(new CustomPaintComponent());

        // Display the frame

        int frameWidth = 300;

        int frameHeight = 300;

        frame.setSize(frameWidth, frameHeight);

        frame.setVisible(true);
 
  }
 
 /**
  * To draw on the screen, it is first necessary to subclass a Component 
  * and override its paint() method. The paint() method is automatically called 
  * by the windowing system whenever component's area needs to be repainted.
  */
  static class CustomPaintComponent extends Component {
 
          public void paint(Graphics g) {

            // Retrieve the graphics context; this object is used to paint shapes

            Graphics2D g2d = (Graphics2D)g;

            // Draw an oval that fills the window

            int x = 0;

            int y = 0;

            int w = getSize().width-1;

            int h = getSize().height-1;

            /**
              * The coordinate system of a graphics context is such that the origin is at the 
              * northwest corner and x-axis increases toward the right while the y-axis increases 
              * toward the bottom.
              */

            g2d.drawLine(x, y, w, h);

            // to draw a filled oval use : g2d.fillOval(x, y, w, h) instead

            g2d.drawOval(x, y, w, h);

            // to draw a filled rectangle use : g2d.fillRect(x, y, w, h) instead

            g2d.drawRect(x, y, w, h);

            // A start angle of 0 represents a 3 o'clock position, 90 represents a 12 o'clock position,

            // and -90 (or 270) represents a 6 o'clock position

            int startAngle = 45;

            int arcAngle = -60;

            // to draw a filled arc use : g2d.fillArc(x, y, w, h, startAngle, arcAngle) instead

            g2d.drawArc(x, y, w/2, h/2, startAngle, arcAngle);

            // to draw a filled round rectangle use : g2d.fillRoundRect(x, y, w, h, arcWidth, arcHeight) instead

            g2d.drawRoundRect(x, y, w, h, w/2, h/2);

            Polygon polygon = new Polygon();

            polygon.addPoint(w/4, h/2);

            polygon.addPoint(0, h/2);

            polygon.addPoint(w/4, 3*h/4);

            polygon.addPoint(w/2, 3*h/4);

            // Add more points...

            // to draw a filled round rectangle use : g2d.fillPolygon(polygon) instead

            g2d.drawPolygon(polygon);

          }
 
  }
 
}