### Question:
RealValue extends Value { @Override Value lessThan (Value v) { return new BooleanValue (mValue < v.toRealValue ().mValue); } RealValue(double value);   RealValue(String value); @Override String toString();  }### Answer:
@Test public void testLessThan () { assertEquals ("true", mNegativeValue.lessThan (mZeroValue).toString ()); assertEquals ("true", mNegativeValue.lessThan (mPositiveValue).toString ()); assertEquals ("true", mZeroValue.lessThan (mPositiveValue).toString ()); assertEquals ("false", mPositiveValue.lessThan (mZeroValue).toString ()); assertEquals ("false", mPositiveValue.lessThan (mNegativeValue).toString ()); assertEquals ("false", mZeroValue.lessThan (mNegativeValue).toString ()); }