Michael Bayne
41f62de088
In anticipation of the saying of nay, I offer this: these are value classes, and in a civilized language, I wouldn't have setters either. "foo.x = x" would call a setter method over which I had control. However, rather than throwing my hands up and saying "Gee, I have to have verbose setters, so I guess I better have verbose getters," I say, "I'll take what I can get." Methods that verb can be verbs, and we can all agree to understand that methods that are nouns are getters. foo.width() does not width my foo, it's my foo's width. foo.invert() inverts up my foo, it is not some attribute of my foo's nonsensically named invert. I don't want to add my foo's getWidth and getHeight, I want to add my foo's width and height. So why should I have to type get over and over again just because I want to protect myself from future representation change? (Or in this case, to offer immutable views of my value classes.)
Pythagoras
Pythagoras is a collection of geometry classes that aims to provide performant,
portable geometry routines for projects that cannot make use of java.awt.geom
(for example for use in GWT projects or Android projects). In addition to
original work, it contains code adapted from the Apache Harmony project and
the Clyde library.
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API documentation is available.
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Pythagoras can be obtained via Maven Central:
com.samskivert:pythagoras:1.0. Or you can download the pre-built jar file.
Design
Some restructuring of the java.awt.geom classes was undertaken to meet
certain design goals.
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The library is specialized on the primitive types rather than attempting to support all types in a single class hierarchy.
pythagoras.fandpythagoras.dprovide equivalent functionality using 32-bit and 64-bit floating point values throughout.pythagoras.iis specialized on int and contains none of the curved geometry classes. -
The need for defensive copying is minimized by the existence of read-only interfaces for each geometric primitive, which allow no mutation of the entity. Thus a consumer that requires only to read the attributes of, for example, a
Rectanglecan accept anIRectangleto indicate to the caller that it will not (and indeed cannot) mutate the supplied entity. Similarly, a read-only interface can be returned to a private internal field without fear that the recipient will mutate it and wreak havoc. Note that the interfaces have a very small, but non-zero, performance cost versus direct use of the mutable classes. Use the interfaces anyway and then profile your application to determine whether there are places where you need to sacrifice code clarity and safety on the altar of higher performance. -
The library supports garbage creation avoidance (for applications which are sensitive to garbage collection pauses, like video games). For example, in cases where entities return a
Rectanglecontaining their bounds, a corresponding method exists which accepts aRectangleinto which to write the bounds. Further work is needed here, as some of the implementation internals create garbage that could be avoided. -
The library attempts to minimize the size of its instances by avoiding the inclusion of any fields that are not essential to the function of a particular geometric entity. For example, no cached hash codes or cached computed bounds are maintained.
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Helper methods associated with a given geometric primitive are separated into a utility class for each primitive. For example line-related primitives are in a class named
Lines.
License
Pythagoras is released under the Apache License, Version 2.0 which can be found
in the LICENSE file and at http://www.apache.org/licenses/LICENSE-2.0 on the
web.