### Question:
WindowFunction { public double[] applyWindow(double[] data) { calculateWeights(data.length); double[] windowedData = new double[data.length]; for (int i = 0; i < data.length; ++i) { windowedData[i] = windowWeights[i] * data[i]; } return windowedData; } WindowFunction(WindowType type, double parameter);  WindowFunction(WindowType type); double getWindowWeightsSqueredSum(); double[] applyWindow(double[] data);  }### Answer:
@Test public void testApplyWindow() { WindowFunction windowFunction = new WindowFunction(WindowType.BARTLETT); windowFunction.calculateWeights(10); double[] windowWeights = new double[] { 0, 0.22222222, 0.44444444, 0.66666667, 0.88888889, 0.88888889, 0.66666667, 0.44444444, 0.22222222, 0 }; assertArrayEquals(windowWeights, windowFunction.windowWeights, 1e-5); double[] signal = new double[10]; Arrays.fill(signal, 3.0); double[] windowedSignal = windowFunction.applyWindow(signal); double[] expectedWindowedSignal = new double[] { 0, 0.66666667, 1.33333333, 2, 2.66666667, 2.66666667, 2, 1.33333333, 0.66666667, 0 }; assertArrayEquals(expectedWindowedSignal, windowedSignal, 1e-5); }