Java Reference
In-Depth Information
[true]
case
a
case
a actions(s)
break
[false]
[true]
case
b
case
b actions(s)
break
[false]
[true]
case
z
case
z actions(s)
break
[false]
default
actions(s)
Fig. 5.10
|
switch
multiple-selection statement UML activity diagram with
break
statements.
The
break
statement is
not
required for the
switch
's last
case
(or the optional
default
case, when it appears last), because execution continues with the next statement
after the
switch
.
Error-Prevention Tip 5.8
Provide a
default
case in
switch
statements. This focuses you on the need to process ex-
ceptional conditions.
Good Programming Practice 5.3
Although each
case
and the
default
case in a
switch
can occur in any order, place the
de-
fault
case last. When the
default
case is listed last, the
break
for that case is not required.
Notes on the Expression in Each
case
of a
switch
When using the
switch
statement, remember that each
case
must contain a constant inte-
gral expression—that is, any combination of integer constants that evaluates to a constant
integer value (e.g., -7, 0 or 221)—or a
String
. An integer constant is simply an integer val-
ue. In addition, you can use
character constants
—specific characters in single quotes, such
as
'A'
,
'7'
or
'$'
—which represent the integer values of characters and
enum
constants (in-
troduced in Section 6.10). (Appendix B shows the integer values of the characters in the
ASCII character set, which is a subset of the Unicode
®
character set used by Java.)
The expression in each
case
can also be a
constant variable
—a variable containing a
value which does not change for the entire program. Such a variable is declared with key-
word
final
(discussed in Chapter 6). Java has a feature called
enum
types, which we also
present in Chapter 6—
enum
type constants can also be used in
case
labels.
