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POInterfaces with static fields in java for sharing 'constants'
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  1. POInterfaces with static fields in java for sharing 'constants'
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    copied!<p>I'm looking at some open source Java projects to get into Java and notice a lot of them have some sort of 'constants' interface.</p> <p>For instance, <a href="http://www.processing.org" rel="noreferrer">processing.org</a> has an interface called <a href="http://dev.processing.org/source/index.cgi/tags/processing-1.0/core/src/processing/core/PConstants.java?view=markup" rel="noreferrer">PConstants.java</a>, and most other core classes implement this interface. The interface is riddled with static members. Is there a reason for this approach, or is this considered bad practice? Why not use enums <em>where it makes sense</em>, or a static class?</p> <p>I find it strange to use an interface to allow for some sort of pseudo 'global variables'.</p> <pre><code>public interface PConstants { // LOTS OF static fields... static public final int SHINE = 31; // emissive (by default kept black) static public final int ER = 32; static public final int EG = 33; static public final int EB = 34; // has this vertex been lit yet static public final int BEEN_LIT = 35; static public final int VERTEX_FIELD_COUNT = 36; // renderers known to processing.core static final String P2D = "processing.core.PGraphics2D"; static final String P3D = "processing.core.PGraphics3D"; static final String JAVA2D = "processing.core.PGraphicsJava2D"; static final String OPENGL = "processing.opengl.PGraphicsOpenGL"; static final String PDF = "processing.pdf.PGraphicsPDF"; static final String DXF = "processing.dxf.RawDXF"; // platform IDs for PApplet.platform static final int OTHER = 0; static final int WINDOWS = 1; static final int MACOSX = 2; static final int LINUX = 3; static final String[] platformNames = { "other", "windows", "macosx", "linux" }; // and on and on } </code></pre>
 

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