import java.awt.*;
import java.awt.geom.*;
  /**
  * Create Circle
  *
  * @author (Hendra Ramadani 05111740000055)
  *
  * @version (0.0001)
  */
  public class Circle
  {
   private int diameter;
    private int xPosition;
    private int yPosition;
    private String color;
    private boolean isVisible;
   /**
   * Create a new circle at default position with default color.
   */
   public Circle()
   {
       diameter = 30;
       xPosition = 20;
       yPosition = 60;
       color = "blue";
       isVisible = false;
   }
    /**
     * Make this circle visible. If it was already visible, do nothing.
     */
    public void makeVisible()
    {
       isVisible = true;
       draw();
    }
    /**
     * Make this circle invisible. If it was already invisible, do nothing.
     */
    public void makeInvisible()
    {
       erase();
       isVisible = false;
    }
   /**
   * Move the circle a few pixels to the right.
   */
   public void moveRight()
   {
       moveHorizontal(20);
   }
   /**
   * Move the circle a few pixels to the left.
   */
   public void moveLeft()
   {
       moveHorizontal(-20);
   }
   /**
   * Move the circle a few pixels up.
   */
   public void moveUp()
   {
       moveVertical(-20);
   }
   /**
   * Move the circle a few pixels down.
   */
   public void moveDown()
   {
       moveVertical(20);
   }
   /**
   * Move the circle horizontally by 'distance' pixels.
   */
   public void moveHorizontal(int distance)
   {
       erase();
       xPosition += distance;
       draw();
   }
   /**
   * Move the circle vertically by 'distance' pixels.
   */
   public void moveVertical(int distance)
   {
       erase();
       yPosition += distance;
       draw();
   }
   /**
   * Slowly move the circle horizontally by 'distance' pixels.
   */
   public void slowMoveHorizontal(int distance)
   {
       int delta;
       if(distance < 0)
       {
         delta = -1;
         distance = -distance;
       }
       else
       {
         delta = 1;
       }
       for(int i = 0; i < distance; i++)
       {
         xPosition += delta;
         draw();
       }
   }
   /**
   * Slowly move the circle vertically by 'distance' pixels.
   */
   public void slowMoveVertical(int distance)
   {
       int delta;
       if(distance < 0)
       {
         delta = -1;
         distance = -distance;
       }
       else
       {
         delta = 1;
       }
       for(int i = 0; i < distance; i++)
       {
         yPosition += delta;
         draw();
       }
   }
   /**
   * Change the size to the new size (in pixels). Size must be >= 0.
   */
   public void changeSize(int newDiameter)
   {
       erase();
       diameter = newDiameter;
       draw();
   }
   /**
   * Change the color. Valid colors are "red", "yellow", "blue", "green",
     * "magenta" and "black".
   */
   public void changeColor(String newColor)
   {
       color = newColor;
       draw();
   }
    /*
     * Draw the circle with current specifications on screen.
     */
    private void draw()
    {
       if(isVisible) {
         Canvas canvas = Canvas.getCanvas();
         canvas.draw(this, color, new Ellipse2D.Double(xPosition, yPosition, diameter, diameter));
         canvas.wait(10);
       }
    }
    /*
     * Erase the circle on screen.
     */
    private void erase()
    {
       if(isVisible) {
         Canvas canvas = Canvas.getCanvas();
         canvas.erase(this);
       }
    }
  }