以下代码段未产生预期结果

Question

I found this in one of the Java programming quiz question.

 public class Calculator { public static void main(String[] args) { int i = 0; Calculator c = new Calculator(); System.out.print(i++ + c.opearation(i)); System.out.print(i); } public int operation(int i) { System.out.print(i++); return i; } } 

Executing above snippet gives me the result of 121 . I'm expecting it to be 111 . I'll explain how I interpreted it.

+ addition operator would get executed from right to left (ref: operator precedence ). So, c.operation(0) is invoked first and it prints the value 1 instead I'm expecting the value to be 0 since System.out.print prints the value of i first and then increments the i value since it is a post increment operator.

Secondly, the i value 1 is returned to the main and the statement System.out.print(i++ + 1) gets executed now. And since i has post increment operator it should have executed like 0 + 1 and produced the result 1 insted it printed result as 2 .

Thirdly, the i value is now incremented to 1 and this gets printed as expected.

In short, I'm expecting the value to be printed as 011 but I got the result as 121 . I'm not sure where my interpretation goes wrong.

Answer 1

Additive Operators

The additive operators have the same precedence and are syntactically left-associative (they group left-to-right).

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int i = 0;
System.out.print(i++ + c.operation(i));

1. evaluate i++ , get left operand 0 , and increment i to 1 .

2. pass i(1) to c.operation(i) , execute System.out.print(i++) . Print 1 then return 2 (right operand).

3. i++ + c.operation(i) ---> 0 + 2 , print 2 .

4. print 1 .