Data and Expressions - Java Software Solutions: Foundations of Program Design - page 81

count currently contains the value 15 , the following statement assigns the value
15 to total and the value 16 to count :
total = count++;
However, the following statement assigns the value 16 to both total and count :
total = ++count;
The value of count is incremented in both situations, but the value used in the
larger expression depends on whether a prefix or postfix form of the increment
operator is used.
Because of the subtle differences between the prefix and postfix forms of the
increment and decrement operators, they should be used with care. As always,
favor the side of readability.
Assignment Operators
As a convenience, several assignment operators have been defined in Java that
combine a basic operation with assignment. For example, the += operator can be
used as follows:
total += 5;
This performs the same operation as the following statement:
total = total + 5;
The right-hand side of the assignment operator can be a full expression. The
expression on the right-hand side of the operator is evaluated, then that result is
added to the current value of the variable on the left-hand side, and that value is
stored in the variable. Therefore, the following statement:
total += (sum - 12) / count;
is equivalent to:
total = total + ((sum - 12) / count);
Many similar assignment operators are defined in Java, including those that
perform subtraction ( -= ), multiplication ( *= ), division ( /= ), and remainder ( %= ).
The entire set of Java operators is discussed in Appendix D.
All of the assignment operators evaluate the entire expression on the right-
hand side first, then use the result as the right operand of the other operation.
Therefore, the following statement:
result *= count1 + count2;