### Question:
RealValue extends Value { @Override Value multiply (Value v) { return new RealValue (mValue * v.toRealValue ().mValue); } RealValue(double value);   RealValue(String value); @Override String toString();  }### Answer:
@Test public void testMultiply () { assertEquals ("0", mZeroValue.multiply (mPositiveValue).toString ()); assertEquals ("1,23", mOneValue.multiply (mPositiveValue).toString ()); assertEquals ("-1,23", mMinusOneValue.multiply (mPositiveValue).toString ()); assertEquals ("1,23", mMinusOneValue.multiply (mNegativeValue).toString ()); }