I\'ve misplaced += with =+ one too many times, and I think I keep forgetting because I don\'t know the difference between these two, only that one
+=
=+
a += b is short-hand for a = a + b (though note that the expression a will only be evaluated once.)
a += b
a = a + b
a
a =+ b is a = (+b), i.e. assigning the unary + of b to a.
a =+ b
a = (+b)
+
b
Examples:
int a = 15; int b = -5; a += b; // a is now 10 a =+ b; // a is now -5