java - Why can I add characters to strings but not characters to characters?

Question

So I wanted to add a character to a string, and in some cases wanted to double that characters then add it to a string (i.e. add to it itself first). I tried this as shown below.

char s = 'X'; 
String string = s + s;

This threw up an error, but I'd already added a single character to a string so I tried:

String string = "" + s + s;

Which worked. Why does the inclusion of a string in the summation cause it to work? Is adding a string property which can only be used by characters when they're converted to strings due to the presence of a string?

Answer 1

It's because String + Char = String, similar to how an int + double = double.

Char + Char is int despite what the other answers tell you.

String s = 1; // compilation error due to mismatched types.

Your working code is (String+Char)+Char. If you had done this: String+(Char+Char) you would get a number in your string. Example:

System.out.println("" + ('x' + 'x')); // prints 240
System.out.println(("" + 'x') + 'x'); // prints xx - this is the same as leaving out the ( ).