I've seen some of this symbols, but I cannot find anything strange with it,
double d = 5D;
float f = 3.0F;
What does the D and F behind 5 exactly means?
Means that these numbers are doubles and floats, respectively. Assume you have
void foo(int x);
void foo(float x);
void foo(double x);
and then you call
foo(5)
the compiler might be stumped. That's why you can say 5
, 5f
, or 5.0
to specify the type.