IntegerValue implements Value<Integer> { @Override public String toString() { return value == null ? "null" : value.toString(); } IntegerValue(Integer value); @Override Double getDouble(); @Override Integer getValue(); @Override void setValue(Integer value); @Override int compareTo(Value<Integer> arg); @Override int hashCode(); @Override boolean equals(Object obj); @Override String toString();  }
@Test public void toStringTest() { IntegerValue dnull = new IntegerValue(null); IntegerValue d1 = new IntegerValue(1); Assert.assertEquals("null", dnull.toString()); Assert.assertEquals("1", d1.toString()); }