Java arithmetic operators ,Please explain the output

Question

public class MainClass
{

     public static void main(String[] args)
     {
        int i = 13 - - 14 + + 15;
        // evaluate this as Right to Left associativity 
        // so (13 - (-14)) + + 15 = 27 + +15 = 42 --> correct 
        System.out.println(i);
     }
}

Since + and - has same precedence , so it will have right to left associativity. So I thought that any expression like 13 - - 14 + + 15 will be considered as 13 - (-14 + + 15) and output will be 12, but output is coming 42. Can anyone please explain the output?

Left-to-right associativity means that A op B op C is (A op B) op C, not A op (B op C). — Oliver Charlesworth
– Oliver Charlesworth, Commented Apr 3, 2015 at 11:12
Thanks Oliver!! I have edited the question. + and - operator has right to left associativity. — DevCoder
– DevCoder, Commented Apr 3, 2015 at 11:54
The unary operators are right-to-left; the binary operators (i.e. addition and subtraction) are left-to-right. — Oliver Charlesworth
– Oliver Charlesworth, Commented Apr 3, 2015 at 11:56

Moishe Lipsker · Accepted Answer · 2015-04-03 11:13:39Z

2

You can look at 13 - - 14 + + 15 like 13 - (-14), which is like 13 + 14, which is 27, followed by + (+ 15), which is like + 15, which equals 42.

answered Apr 3, 2015 at 11:13

Moishe Lipsker

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Comments

Eran · Accepted Answer · 2015-04-03 11:11:42Z

1

If you evaluate the expression from left to right (as Java does), you start with 13 - - 14 which is the same as 13 - (-14), which is 27. 27+ +15 is 42.

answered Apr 3, 2015 at 11:11

Eran

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aniri · Accepted Answer · 2015-04-03 11:12:55Z

0

Evaluating from left to right it's 13 - (-14) + (+15) so 13 + 14 + 15 = 42

answered Apr 3, 2015 at 11:12

aniri

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