Explain Switch Statement In Java, Switch Statement With Program And Example Explain In Java
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switch
The switch statement is Java’s multiway branch statement. It provides an easy way to dispatch
execution to different parts of your code based on the value of an expression. As such, it often
provides a better alternative than a large series of
if-else-if
statements. Here is the general form
of a
switch
statement:
switch ( expression ) {
case value1 :
// statement sequence
break;
case value2 :
// statement sequence
break;
.
.
.
case valueN :
// statement sequence
break;
default:
// default statement sequence
}
The expression must be of type
byte short int
,
,
, or
char
; each of the values specified in the
case
statements must be of a type compatible with the expression. (An enumeration value can
also be used to control a
switch
statement. Enumerations are described in Chapter 12.) Each
case
value must be a unique literal (that is, it must be a constant, not a variable). Duplicate
case
values are not allowed.
The
switch
statement works like this: The value of the expression is compared with each
of the literal values in the
case
statements. If a match is found, the code sequence following
that
case
statement is executed. If none of the constants matches the value of the expression,
then the
default
statement is executed. However, the
default
statement is optional. If no
case
matches and no
default
is present, then no further action is taken.
The
break
statement is used inside the
switch
to terminate a statement sequence. When
a
break
statement is encountered, execution branches to the first line of code that follows the
entire
switch
statement. This has the effect of “jumping out” of the
switch
.
Here is a simple example that uses a
switch
statement:
// A simple example of the switch.
class SampleSwitch {
public static void main(String args[]) {
for(int i=0; i<6; i++)
switch(i) {
case 0:
System.out.println("i is zero.");
break;
case 1:
System.out.println("i is one.");
break;
case 2:
System.out.println("i is two.");
break;
case 3:
System.out.println("i is three.");
break;
default:
System.out.println("i is greater than 3.");
}
}
}
The output produced by this program is shown here:
i is zero.
i is one.
i is two.
i is three.
i is greater than 3.
i is greater than 3.
As you can see, each time through the loop, the statements associated with the
case
constant
that matches
i
are executed. All others are bypassed. After
i
is greater than 3, no
case
statements
match, so the
default
statement is executed.
The
break
statement is optional. If you omit the
break
, execution will continue on into the
next
case
.
It is sometimes desirable to have multiple
case
s without
break
statements between
them. For example, consider the following program:
// In a switch, break statements are optional.
class MissingBreak {
public static void main(String args[]) {
for(int i=0; i<12; i++)
switch(i) {
case 0:
case 1:
case 2:
case 3:
case 4:
System.out.println("i is less than 5");
break;
case 5:
case 6:
case 7:
case 8:
case 9:
System.out.println("i is less than 10");
break;
default:
System.out.println("i is 10 or more");
}
}
}
This program generates the following output:
i is less than 5
i is less than 5
i is less than 5
i is less than 5
i is less than 5
i is less than 10
i is less than 10
i is less than 10
i is less than 10
i is less than 10
i is 10 or more
i is 10 or more
As you can see, execution falls through each
case
until a
break
statement (or the end of the
switch
) is reached.
While the preceding example is, of course, contrived for the sake of illustration, omitting the
break
statement has many practical applications in real programs. To sample its more realistic
usage, consider the following rewrite of the season example shown earlier. This version uses a
switch
to provide a more efficient implementation.
// An improved version of the season program.
class Switch {
public static void main(String args[]) {
int month = 4;
String season;
switch (month) {
case 12:
case 1:
case 2:
season = "Winter";
break;
case 3:
case 4:
case 5:
season = "Spring";
break;
case 6:
case 7:
case 8:
season = "Summer";
break;
case 9:
case 10:
case 11:
season = "Autumn";
break;
default:
season = "Bogus Month";
}
System.out.println("April is in the " + season + ".");
}
}