我正在查看一些开放源代码的Java项目以进入Java，并注意到其中许多具有某种“常量”接口。

例如，processing.org有一个名为PConstants.java的接口，大多数其他核心类都实现了该接口。该接口充满了静态成员。是否有这种方法的原因，或者这被认为是不良做法？为什么不使用有意义的枚举或静态类呢？

我发现使用接口允许某种伪“全局变量”很奇怪。

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

}