Documentation

The Java™ Tutorials

Geometric Primitives

The Java 2D API provides a useful set of standard shapes such as points, lines, rectangles, arcs, ellipses, and curves. The most important package to define common geometric primitives is the `java.awt.geom`

package. Arbitrary shapes can be represented by combinations of straight geometric primitives.

The `Shape`

interface represents a geometric shape, which has an outline and an interior. This interface provides a common set of methods for describing and inspecting two-dimensional geometric objects and supports curved line segments and multiple sub-shapes. The
`Graphics`

class supports only straight line segments. The
`Shape`

interface can support curves segments.

For more details about how to draw and fill shapes, see the Working with Geometry lesson.

The `Point2D`

class defines a point representing a location in (x, y) coordinate space. The term “point” in the Java 2D API is not the same as a pixel. A point has no area, does not contain a color, and cannot be rendered.

Points are used to create other shapes. The`Point2D`

class also includes a method for calculating the distance between two points.

The `Line2D`

class is an abstract class that represents a line. A line’s coordinates can be retrieved as double. The `Line2D`

class includes several methods for setting a line’s endpoints.

You can also create a straight line segment by using the `GeneralPath`

class described below.

The `Rectangle2D`

, `RoundRectangle2D`

, `Arc2D`

, and `Ellipse2D`

primitives are all derived from the `RectangularShape`

class. This class defines methods for `Shape`

objects that can be described by a rectangular bounding box. The geometry of a `RectangularShape`

object can be extrapolated from a rectangle that completely encloses the outline of the `Shape`

.

The `QuadCurve2D`

enables you to create quadratic parametric curve segments. A quadratic curve is defined by two endpoints and one control point.

The `CubicCurve2D`

class enables you to create cubic parametric curve segments. A cubic curve is defined by two endpoints and two control points. The following are examples of quadratic and cubic curves. See
Stroking and Filling Graphics Primitivesfor implementations of cubic and quadratic curves.

This figure represents a quadratic curve.

This figure represents a cubic curve.

The `GeneralPath`

class enables you to construct an arbitrary shape by specifying a series of positions along the shape’s boundary. These positions can be connected by line segments, quadratic curves, or cubic (Bézier) curves. The following shape can be created with three line segments and a cubic curve. See
Stroking and Filling Graphics Primitivesfor more information about the implementation of this shape.

With the `Area`

class, you can perform boolean operations, such as union, intersection, and subtraction, on any two `Shape`

objects. This technique, often referred to as *constructive area geometry*, enables you to quickly create complex `Shape`

objects without having to describe each line segment or curve.