SELECTIONS - Introduction to Java Programming: Comprehensive Version - page 101

case value2: statement(s)2;
break ;

...
case valueN: statement(s)N;
break ;
default : statement(s)- for - default ;

}

The switch statement observes the following rules:

The switch-expression must yield a value of char , byte , short , int , or String
type and must always be enclosed in parentheses. (The char and String types will be
introduced in the next chapter.)

■

The value1 , . . ., and valueN must have the same data type as the value of the switch-
expression . Note that value1 , . . ., and valueN are constant expressions, meaning
that they cannot contain variables, such as 1 + x .

■

■ When the value in a case statement matches the value of the switch-expression ,
the statements starting from this case are executed until either a break statement or the
end of the switch statement is reached.

■ The default case, which is optional, can be used to perform actions when none of the
specified cases matches the switch-expression .

■ The keyword break is optional. The break statement immediately ends the switch
statement.

Caution
Do not forget to use a break statement when one is needed. Once a case is matched,
the statements starting from the matched case are executed until a break statement or
the end of the switch statement is reached. This is referred to as fall-through behavior.
For example, the following code displays Weekdays for day of 1 to 5 and Weekends
for day 0 and 6 .

without break

fall-through behavior

switch (day) {
case 1 :
case 2 :
case 3 :
case 4 :
case 5 : System.out.println( "Weekday" ); break ;
case 0 :
case 6 : System.out.println( "Weekend" );

}

Tip
To avoid programming errors and improve code maintainability, it is a good idea to put
a comment in a case clause if break is purposely omitted.

Now let us write a program to find out the Chinese Zodiac sign for a given year. The
Chinese Zodiac is based on a twelve-year cycle, with each year represented by an animal—
monkey, rooster, dog, pig, rat, ox, tiger, rabbit, dragon, snake, horse, or sheep—in this cycle,
as shown in Figure 3.6.
Note that year % 12 determines the Zodiac sign. 1900 is the year of the rat because 1900
% 12 is 4 . Listing 3.9 gives a program that prompts the user to enter a year and displays the
animal for the year.