### Question:
Arrays { public static double std(int[] X) { return Math.sqrt(cov(X, X)); }  static int sum(int[] array); static double sum(double[] array); static double[] toDouble(int[] array); static double[] log(int[] array); static double[] log(double[] array); static double average(int[] array); static double average(double[] array); static double logaverage(int[] array); static double logaverage(double[] array); static double scalar(double[] x, double[] y); static int max(int[] array); static double max(double[] array); static int min(int[] array); static double min(double[] array); static int argmax(int[] array); static int argmin(int[] array); static double cov(int[] X, int[] Y); static double cov(double[] X, double[] Y); static double std(int[] X); static double std(double[] X);  }### Answer:
@Test public void testStd_intArr() { System.out.println("std"); int[] X = {1, 2, 2, 3}; double expResult = Math.sqrt(0.5); double result = Arrays.std(X); assertEquals(expResult, result, 0.0001); }
@Test public void testStd_doubleArr() { System.out.println("std"); double[] X = {1, 2, 2, 3}; double expResult = Math.sqrt(0.5); double result = Arrays.std(X); assertEquals(expResult, result, 0.0001); }