++i+i++ evaluation

Question

Confusion rose because of this post. The author updated his post, and the result became clear. Conclusion: Java evaluates expressions from left to right

Closed!

As evaluation of expression is done from right to left the following code should store 5 in j:

int i=2;
int j=++i+i++;
System.out.println(j);

But I get 6 as the output, which forces me to re-think the right to left evaluation idea. Kindly explain the theory here.

Answer 1

int i = 2;
int j = ++i + i++;

is the same as

int i = 2;

// This part is from ++i
i = i + 1;
int left = i; // 3

// This part is from i++
int right = i; // 3
i = i + 1;

int j = left + right; // 3 + 3 = 6

If instead you'd done:

int i = 2;
int j = i++ + ++i;

that would be equivalent to:

int i = 2;

// This part is from i++
int left = i; // 2
i = i + 1;

// This part is from ++i
i = i + 1;
int right = i; // 4


int j = left + right; // 2 + 4 = 6

So the sum is the same, but the terms being summed are different.