Rule for Numeric Type Promotion

[Mike Gosling]

Rule 3 of  numeric promotion states:


Smaller data types, namely, byte, short, and char, are first promoted to int any time
they’re used with a Java binary arithmetic operator with a variable (as opposed to a
value), even if neither of the operands is int.

Part in brackets confuses me: (as opposed to a value),

What happens in terms of promotion in following examples:

char c1 = 'a';
char c2 = 'b';

int i1 = c1 + c2; //Here c1 and c2 are promoted to ints?
char c3 = c1 + c2; //How about here?

int i2 = 'a' + 'b'; //There is no promotion?
char c4 = c1 + c2;   //How about here?

[Mihai Mihail]

What I found for c3 and c4 that require to use char values, but c1 and c2 are considered int, but... what about to use Strings?

[Ankit Garg]

int i1 = c1 + c2; //Here c1 and c2 are promoted to ints?
char c3 = c1 + c2; //How about here?

You are right, c1 and c2 will be promoted to int, that's why the 2nd line won't compile.

int i2 = 'a' + 'b'; //There is no promotion?
char c4 = c1 + c2;   //How about here?

Here I'm assuming you wanted to write char ch4 = 'a' + 'b'; which does compile i.e. the literal values are not promoted to int.