### Question:
PowerFunction2D implements Function2D, Serializable { @Override public int hashCode() { int result = 29; result = HashUtilities.hashCode(result, this.a); result = HashUtilities.hashCode(result, this.b); return result; } PowerFunction2D(double a, double b); double getA(); double getB(); @Override double getValue(double x); @Override boolean equals(Object obj); @Override int hashCode();  }### Answer:
@Test public void testHashCode() { PowerFunction2D f1 = new PowerFunction2D(1.0, 2.0); PowerFunction2D f2 = new PowerFunction2D(1.0, 2.0); assertEquals(f1.hashCode(), f2.hashCode()); }