Forward references to variables gives a compiler error
Even before b is initialized , a is trying to access it. ERROR. However forward reference id possible in somecase.
All comparisons involving NaN and a non-NaN always result in false.
NaN is defined in Double and Float as,
public static final float NaN = 0.0f / 0.0f; (Float class)
public static final double NaN = 0.0d / 0.0; (Double class)
Except != operator all other comparision results in false.
You can never cast objects of sibling classes (sharing the same parent).
Results in error because C & B does not share any relation directly.