Question

While working with Kent Becks Book TDD by Example, I encountered some Java Code I did not understand.

public boolean equals(Object object) {
    Dollar dollar= (Dollar) object;
    return amount == dollar.amount;
}

Could someone please explain to me what the parenthesis in Dollar dollar= (Dollar) object; mean?

Answer 1

It’s an explicit typecast. Basically it’s saying that “although ‘object’ was declared with type Object, I know that it’s actually of type Dollar so it’s okay to assign it to the variable ‘dollar'”.

Without the brackets (actually, those are parenthesis, brackets look like [] or <> depending if they are “square brackets” or “angle brackets”, respectively), the compiler would report an error on that line.