Problem while printing characters Difference between System.out.println('A') and System.out.println(+'A') [closed]

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Why is it that :

 System.out.println(+'A')   //gives output as 65

  System.out.println('A')   //gives output as A

Also

 System.out.println(8+4+'A'+"PRIME"+4+4+'A');

gives output as 77PRIME44A

Why is it that 8+4 before the String "Prime" are being added, while 4+4 after "Prime" are being printed as it is ?

I also have a doubt why 8+4+'A' results in 65(ascii of A)+12=77 whereas 4+4+'A' doesn't include A's ascii getting added up ?

Is there any specific rule or convention regarding the above ?

Answer 1

System.out.println(+'A') //gives output as 65

In the expression +'A' the unary plus operator (indicating a positive integer) gets applied to 'A' and the expression only makes sense if the char is converted to an int. The character 'A' has the int value of 65 (see the ASCII table), which is why the whole expression evaluates to 65, which then gets printed.

System.out.println(8+4+'A'+"PRIME"+4+4+'A');

gives output as 77PRIME44A

Why is it that 8+4 before the String "Prime" are being added, while 4+4 after "Prime" are being printed as it is ?

Because the associativity of + (both for integer addition and for string concatenation) is left-to-right. So first you do 8+4, which is integer addition, then 12+'A' (which requires 'A' to be interpreted as its integer value 65), and then you have +"PRIME". But this only makes sense as string concatenation, which is why it results in "77PRIME"; afterwards every call to + is a string concatenation; the integers get converted to their string equivalents (4 -> "4") and the result of a string + char operation shouldn't surprise you.

So it's

8+4+'A'+"PRIME"+4+4+'A' 
--> ((((((8+4)+'A')+"PRIME")+4)+4)+'A')    // placed explicit parenthesis
--> (((((12+'A')+"PRIME")+4)+4)+'A')       // int addition 8+4
--> ((((77+"PRIME")+4)+4)+'A')             // int addition, 'A' cast to int 65
--> ((("77PRIME")+4)+4)+'A')               // string concat, 77 converted to "77"
--> (("77PRIME4"+4)+'A')                   // string concat, 4 --> "4"
--> ("77PRIME44"+'A')                      // ditto
--> "77PRIME44A"                           // string + char concat