char and int in Java

Question

I was surprised to see this code work. I thought that char and int were two distinct data types in Java and that I would have had to cast the char to an int for this to give the ascii equivelent. Why does this work?

String s = "hello";
int x = s.charAt(1);
System.out.println(x);

Answer 1

A char can be automatically converted to an int. See JLS 5.1.2:

The following 19 specific conversions on primitive types are called the widening primitive conversions:

...

• char to int, long, float, or double

...

A widening conversion of a signed integer value to an integral type T simply sign-extends the two's-complement representation of the integer value to fill the wider format. A widening conversion of a char to an integral type T zero-extends the representation of the char value to fill the wider format.

(emphasis added)