Rectangle2D

Rectangle2D is an abstract class in the Java 2D API (java.awt.geom) that represents an axis-aligned rectangle defined by its position and size. It specifies a rectangle in user space using coordinates for the top-left corner along with a width and height. As part of the RectangularShape hierarchy, Rectangle2D provides accessors for the rectangle’s geometry and supports basic geometric operations used in rendering and hit testing.

In practice, Rectangle2D is typically used through its two public concrete subclasses: Rectangle2D.Double, which stores coordinates and dimensions as double precision, and Rectangle2D.Float, which uses float precision. This distinction allows developers to balance precision and memory usage according to the application's needs. Common operations exposed by the class and its superclasses include querying the rectangle’s bounds (x, y, width, height), testing containment (whether a point or another rectangle lies inside the rectangle), and testing intersection with other shapes. The class also supports modifying the frame through setters and frame-adjustment methods.

Rectangle2D is frequently employed as a bounding box for components, shapes, or images in Java 2D graphics. It is also used in clipping, rendering optimizations, and collision or hit-testing logic within graphical applications. The coordinate system used by Java graphics places the origin at the top-left, with the x-axis extending to the right and the y-axis extending downward, which influences how width and height are interpreted.

Overall, Rectangle2D provides a compact, performance-oriented primitive for representing and manipulating rectangular regions in 2D graphics work.