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Rule for Numeric Type Promotion

 
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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?
 
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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?
 
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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.
 
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