What is the order this code compiles?

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I'm interested in the order 'b' is calculated here: int a = 3; int b = a++ + (a-- * a++); We've read in the lesson that the 1st priority belongs to parenthesis, so we begin with (a-- * a++), right? The 2nd priority is the unary operator, but which one? The lesson says it works from right to left. Does that mean I should first do the a++ in the parenthesis? When I increment it, do I use the incremented value in the 'a--' part, or do I save it just in case? Why is the output 15, not 16 then?

package en.codegym.task.pro.task08.task0817; /* Increments */ public class Solution { public static void main(String[] args) { int a = 3; int b = a++ + (a-- * a++); // b = (3+1) + ((3-1)*(3+1)); System.out.println(b); //System.out.println(a); } }

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Thomas

Level 41 , Bayreuth, Germany

11 April, 12:00

Equal precedence operators evaluation order is from left to right. There is one exception. Assignment operators are evaluated from right to left (like a = b = c = 1) The postfix operator has the highest precedence. Means it is evaluated first, even before the parenthesis. It just has a weird way to behave. If you have eg. int a = 1; int b = a++ + a++; then the first thing happening is the evaluation of the postfix expressions. Internally it is similar to copying the current value of a into a temp variable t and then a is incremented. int b = t + a++; // t = 1, the value of a before incrementation and a gets incremented to 2 int b = 1 + a++; // now the same for the second postfix increment, a temp variable u with the value of a's current value is created and used where the postfix expression is. a is incremented by 1 int b = 1 + 2; // while a is now 3 in the above example it should be int a = 3; int b = a++ + (a-- * a++); int b = 3 + (a-- * a++); // left to right, current value of a inserted, a incremented to 4 int b = 3 + (4 * a++); // current value of a inserted, that's 4 and a decremented to 3 int b = 3 + (4 * 3); // current value 3 inserted, a incremented to 4 int b = 15; // a == 4 PS: hah, checked your the output of your code and it is correct ;)

Evgeniia Shabaeva

Level 11 , Budapest, Hungary

12 April, 09:10

Thank you very much. In this task I was supposed to rewrite the code so it produced '20' as a result (and I kind of did it, but it was merely a wild guess in my case). So I wanted to better understand how the algorithm works, and now I feel I do. Thank you once again.