Question

This is something I never truly understood in Java. Lets say I have:

int x = 4;

now I can not do this

functionThatRequiresString(x) or functionThatRequiresString((String)x)

Now I can not pass a function that requires a string the variable x. I am also unable to cast it from an int to a string. Now the normal ways of doing this would be:

Integer.toString(x) or String.valueOf(x)

Now why can I do this though?

functionThatRequiresString(""+x)

How is this different from casting an integer to a string?

Answer 1

Casting means that you tell the compiler “I have an object of type A here, but I want you to treat it as if it is of type B. Don’t give an error because it doesn’t look like a B to you”.

Casting does not do any conversions (at least not for non-primitive types). If, when running the program, the object really is not of type B, you will get a ClassCastException.

You cannot cast an int to a String because an int is simply not a String – you can tell the compiler to pretend that it is, but you’ll get a ClassCastException when you run the program.

The other examples you give will convert (not cast) an int to a String.