Puzzle (Tweedledee)

Contrariwise, provide declarations for the variables x and i such that this is a legal statement:

x = x + i;

but this is not:

x += i;

At first glance, this puzzle might appear to be the same as the previous one. Rest assured, it’s different.

This example was taken from PUZZLE 10: TWEEDLEDEE in Java™ Puzzlers: Traps, Pitfalls, and Corner Cases.

“Compound assignment operators require both operands to be primitives, such as int, or boxed primitives, such as Integer, with one exception: The += operator allows its right-hand operand to be of any type if the variable on the left-hand side is of type String, in which case the operator performs string concatenation (JLS 15.26.2). The simple assignment operator (=) is much less picky when it comes to allowing object reference types on the left-hand side: You can use them to your heart’s content so long as the expression on the right-hand side is assignment compatible with the variable on the left (JLS 5.2).”