Question

What are the order of operations when using two assignment operators in a single line?

public static void main(String[] args){
    int i = 0;
    int[] a = {3, 6};
    a[i] = i = 9; // this line in particular
    System.out.println(i + " " + a[0] + " " + a[1]);
}

Edit: Thanks for the posts. I get that = takes values from the right, but when I compile this I get:

9 9 6

I thought it would have been and ArrayOutOfBounds exception, but it is assigning ‘a[i]’ before it’s moving over the 9. Does it just do that for arrays?

Answer 1

= is parsed as right-associative, but order of evaluation is left-to-right.

So: The statement is parsed as a[i] = (i = 9). However, the expression i in a[i] is evaluated before the right hand side (i = 9), when i is still 0.

It’s the equivalent of something like:

int[] #0 = a;
int #1 = i;
int #2 = 9;
i = #2;
#0[#1] = #2;