Java Reference
In-Depth Information
6. On your own, try modifying the program so that it uses and displays 1's and 0's,
rather than true and false. This may involve a bit more effort than you might at first
think!
Expressions
Operators, variables, and literals are constituents of expressions . You probably already
know the general form of an expression from your other programming experience, or from
algebra. However, a few aspects of expressions will be discussed now.
Type Conversion in Expressions
Within an expression, it is possible to mix two or more different types of data as long as
they are compatible with each other. For example, you can mix short and long within an
expression because they are both numeric types. When different types of data are mixed
within an expression, they are all converted to the same type. This is accomplished through
the use of Java's type promotion rules .
First, all char , byte , and short values are promoted to int . Then, if one operand is a long ,
the whole expression is promoted to long . If one operand is a float operand, the entire ex-
pression is promoted to float . If any of the operands is double , the result is double .
It is important to understand that type promotions apply only to the values operated upon
when an expression is evaluated. For example, if the value of a byte variable is promoted
to int inside an expression, outside the expression, the variable is still a byte . Type promo-
tion only affects the evaluation of an expression.
Type promotion can, however, lead to somewhat unexpected results. For example, when
an arithmetic operation involves two byte values, the following sequence occurs: First, the
byte operands are promoted to int . Then the operation takes place, yielding an int result.
Thus, the outcome of an operation involving two byte values will be an int . This is not
what you might intuitively expect. Consider the following program:
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