Java Print

Question

Hi all!
I've found this code on Challenge questions but I have no clue what is happening.

int a = 10;
int b = 20;

System.out.print(a + b + “ “ + a + b);

Why is the output 30 1020 and not 30 30 ?
What does double quote make to the print so that no addition is made?
Thx in advance :)

Answer 1

Nice one. Well indeed it's due to the + operator.

When it evaluates what's inside the parentheses, it sees :
- a + b : the addition of two int (let's call it c)
- c + " " : an int and a String -> convert the int into a String and add the String's (let's call the result s)
- s + a : a String and an int -> same as before : converts the int into a String and add them together
- the last one (+b) works exactly the same way as the previous ones.

A way to obtains 30 30 is to write :

System.out.println(a + b + " " + (a + b));

By putting the second "a+b" in parentheses, we change the order of evaluation and this leads to adding them together before adding them to a String

Answer 2

The " " is of string type, rather than int. Because math deals with numbers, rather than strings, the string is causing it to implicitly typecast the rest of it as a string rather than keeping them as an int. So now the " " + a + b are all strings, it's simply concatenating it, which is why you get 1020 for that portion of it.

Hope that helps!

Answer 3

Thank you both! rly appreciate it

Answer 4

You're welcome !