The difference between += and =+

Solution 1:

a += b is short-hand for a = a + b (though note that the expression a will only be evaluated once.)

a =+ b is a = (+b), i.e. assigning the unary + of b to a.

Examples:

int a = 15;
int b = -5;

a += b; // a is now 10
a =+ b; // a is now -5

Solution 2:

+= is a compound assignment operator - it adds the RHS operand to the existing value of the LHS operand.

=+ is just the assignment operator followed by the unary + operator. It sets the value of the LHS operand to the value of the RHS operand:

int x = 10;

x += 10; // x = x + 10; i.e. x = 20

x =+ 5; // Equivalent to x = +5, so x = 5.

Solution 3:

+= → Add the right side to the left

=+ → Don't use this. Set the left to the right side.

Solution 4:

a += b equals a = a + b. a =+ b equals a = (+b).

Solution 5:

x += y 

is the same as

x = x + y

and

x =+ y

is wrong but could be interpreted as

x = 0 + y