Compound Assignment Operators

Java provides several compound assignment operators for abbreviating assignment expressions. Any statement of the form

variable = variable operator expression;

where operator is one of the binary operators +, -, *, / or % (or others we discuss later in the text) can be written in the form

variable operator= expression;

For example, you can abbreviate the statement

 c = c + 3;

with the addition compound assignment operator, +=, as

 c += 3;

The += operator adds the value of the expression on the right of the operator to the value of the variable on the left of the operator and stores the result in the variable on the left of the operator. Thus, the assignment expression c += 3 adds 3 to c. Figure 4.14 shows the arithmetic compound assignment operators, sample expressions using the operators and explanations of what the operators do.

Figure 4.14. Arithmetic compound assignment operators.

Assignment operator	Sample expression	Explanation	Assigns
Assume: int c = 3, d = 5, e = 4, f = 6, g = 12;
+=	c += 7	c = c + 7	10 to c
-=	d -= 4	d = d - 4	1 to d
*=	e *= 5	e = e * 5	20 to e
/=	f /= 3	f = f / 3	2 to f
%=	g %= 9	g = g % 9	3 to g