Learning Java

A Quick Tour of Java 2D

Filling Shapes

The simplest path through the rendering pipeline is for filling shapes. For example, the following code creates an ellipse and fills it with a solid color. (This code would live inside a paint( ) method somewhere. We’ll present a complete, ready-to-run example a little later.)

Shape c = new Ellipse2D.Float(50, 25, 150, 150);
g2.setPaint(Color.blue);
g2.fill(c);

The Ellipse2D class is abstract, but is implemented by concrete inner subclasses, called Float and Double. The Rectangle2D class, for example, has concrete subclasses Rectangle2D.Float and Rectangle2D.Double.

In the call to setPaint( ), we tell the Graphics2D to use a solid color, blue, for all subsequent filling operations. Then, the call to fill( ) tells Graphics2D to fill the given shape.

All geometric shapes in the 2D API are represented by implementations of the java.awt.geom.Shape interface. This interface defines methods that are common to all shapes, like returning a rectangle bounding box or testing if a point is inside the shape. The java.awt.geom package is a smorgasbord of useful shape classes, including Rectangle2D, RoundRectangle2D (a rectangle with rounded corners), Arc2D, Ellipse2D, and others. In addition, a few classes in java.awt are Shapes: Rectangle, Polygon, and Area.

Drawing Shape Outlines

Drawing a shape’s outline is only a little bit more complicated. Consider this example:

Shape r = new Rectangle2D.Float(100, 75, 100, 100); g2.setStroke(new BasicStroke(4)); ...