Getting Started - Java - page 24

combined. If both operands (that is, both numbers) are of type int , then the result of
combining them with an arithmetic operator is of type int . If one, or both, of the
operands is of type double , then the result is of type double . For example, if the vari-
ables baseAmount and increase are both of type int , then the number produced by
the following expression is of type int :
baseAmount + increase
However, if one, or both, of the two variables is of type double , then the result is of
type double . This is also true if you replace the operator + with any of the operators − ,
* , / , or % .
More generally, you can combine any of the arithmetic types in expressions. If all
the types are integer types, the result will be the integer type. If at least one of the sub-
expressions is of a floating-point type, the result will be a floating-point type.
Knowing whether the value produced is of an integer type or a floating-point type
is typically all that you need to know. However, if you need to know the exact type of
the value produced by an arithmetic expression, it can be determined as follows: The
type of the value produced is one of the types used in the expression. Of all the types
used in the expression, it is, with rare exceptions, the last type (reading left to right) on
the following list:
byte —> short —> int —> long —> float —> double
Here are the rare exceptions: Of all the types used in the expression, if the last type
(reading left to right) is byte or short , then the type of the value produced is int . In
other words, an expression never evaluates to either of the types byte or short . These
exceptions have to do with an implementation detail that need not concern us, espe-
cially since we almost never use the types byte and short in this topic.
Note that this sequence of types is the same sequence of types we saw when discuss-
ing assignment compatibility. As you go from left to right, the types increase in the
range of values they allow. 5
Parentheses and Precedence Rules ★
If you want to specify exactly what subexpressions are combined with each operator,
you can fully parenthesize an expression. For example:
((base + (rate * hours))/(2 + rate))
If you omit some parentheses in an arithmetic expression, Java will, in effect, put in
parentheses for you. When adding parentheses, Java follows rules called precedence
5 Although we discourage the practice, you can use values and variables of type char in arithmetic
expressions using operators such as + . If you do so, the char values and variables will contribute to
the expression as if they were of type int .