### Question:
NormalDistributionFunction2D implements Function2D, Serializable { @Override public int hashCode() { int result = 29; result = HashUtils.hashCode(result, this.mean); result = HashUtils.hashCode(result, this.std); return result; } NormalDistributionFunction2D(double mean, double std); double getMean(); double getStandardDeviation(); @Override double getValue(double x); @Override boolean equals(Object obj); @Override int hashCode();  }### Answer:
@Test public void testHashCode() { NormalDistributionFunction2D f1 = new NormalDistributionFunction2D(1.0, 2.0); NormalDistributionFunction2D f2 = new NormalDistributionFunction2D(1.0, 2.0); assertEquals(f1.hashCode(), f2.hashCode()); }