### Question:
NumberTickUnit extends TickUnit implements Serializable { @Override public int hashCode() { int result = super.hashCode(); result = 29 * result + (this.formatter != null ? this.formatter.hashCode() : 0); return result; } NumberTickUnit(double size);  NumberTickUnit(double size, NumberFormat formatter);  NumberTickUnit(double size, NumberFormat formatter,
            int minorTickCount); @Override String valueToString(double value); @Override boolean equals(Object obj); @Override String toString(); @Override int hashCode();  }### Answer:
@Test public void testHashCode() { NumberTickUnit t1 = new NumberTickUnit(1.23, new DecimalFormat("0.00")); NumberTickUnit t2 = new NumberTickUnit(1.23, new DecimalFormat("0.00")); int h1 = t1.hashCode(); int h2 = t2.hashCode(); assertEquals(h1, h2); }