### Question:
UtilColor { public static double getDelta(ColorRgba a, ColorRgba b) { Check.notNull(a); Check.notNull(b); final int dr = a.getRed() - b.getRed(); final int dg = a.getGreen() - b.getGreen(); final int db = a.getBlue() - b.getBlue(); return Math.sqrt(dr * dr + dg * dg + db * db); } private  UtilColor(); static int getRgbaValue(int r, int g, int b, int a); static int multiplyRgb(int rgb, double fr, double fg, double fb); static int inc(int value, int r, int g, int b); static double getDelta(ColorRgba a, ColorRgba b); static ColorRgba getWeightedColor(ImageBuffer surface, int sx, int sy, int width, int height); static boolean isOpaqueTransparentExclusive(ColorRgba colorA, ColorRgba colorB); static boolean isOpaqueTransparentExclusive(int colorA, int colorB);  }### Answer:
@Test void testDelta() { assertEquals(Math.sqrt(255 * 255 + 255 * 255 + 255 * 255), UtilColor.getDelta(ColorRgba.BLACK, ColorRgba.WHITE)); assertEquals(0.0, UtilColor.getDelta(ColorRgba.GRAY, ColorRgba.GRAY)); }