The switch statement is used to evaluate a variable or an expression against a set of constant values and execute different statements based on the matching value. The switch statement provides a more concise way of testing a variable against multiple values than using a series of if-else statements.
The basic syntax of the switch statement is as follows:
switch (variable) {
case value1:
// statement(s) to execute if variable is equal to value1
break;
case value2:
// statement(s) to execute if variable is equal to value2
break;
case value3:
// statement(s) to execute if variable is equal to value3
break;
// more cases can be added here
default:
// statement(s) to execute if none of the above cases match
}
The switch statement evaluates the value of the variable against the case labels, which are constant values. If a matching case is found, the statements inside that case are executed until the break statement is encountered, which exits the switch block. If none of the case labels match the value of the variable, the statements inside the default the block is executed.
Here’s an example that demonstrates the use of the switch statement:
int dayOfWeek = 4;
String dayName;
switch (dayOfWeek) {
case 1:
dayName = "Sunday";
break;
case 2:
dayName = "Monday";
break;
case 3:
dayName = "Tuesday";
break;
case 4:
dayName = "Wednesday";
break;
case 5:
dayName = "Thursday";
break;
case 6:
dayName = "Friday";
break;
case 7:
dayName = "Saturday";
break;
default:
dayName = "Invalid day";
}
System.out.println("Today is " + dayName);
In this example, the program uses a switch statement to determine the name of the day based on the dayOfWeek variable. Since the value of dayOfWeek is 4, the case 4 label matches and the program assigns "Wednesday" to the dayName variable. Finally, the program prints out "Today is Wednesday".
Fall through
Fall through refers to the behavior where the control flow of the program continues to the next case label after the matching case label, even if there is no break statement.
Here’s an example that demonstrates the fall through behavior in a switch statement:
int num = 2;
String numWord;
switch (num) {
case 1:
case 2:
case 3:
numWord = "small";
break;
case 4:
case 5:
case 6:
numWord = "medium";
break;
case 7:
case 8:
case 9:
numWord = "large";
break;
default:
numWord = "unknown";
}
System.out.println(num + " is a " + numWord + " number.");
In this example, the program uses a switch statement to determine whether a given num is small, medium, or large. The first case label matches for num values of 1, 2, or 3. Instead of using a break statement at the end of the case block, the control flow falls through to the next case label. The second case label matches for num values of 4, 5, or 6, and so on.
If there is no break statement at the end of a case block and the control flow falls through to the next case label, the statements in that case block are also executed, even if the value of the variable does not match that case label. For example, if num were 2, both the case 1 and case 2 blocks would be executed, even though the value of num only matches case 2.
Therefore, it is important to be aware of the fall through behavior and use break statements appropriately in a switch statement to avoid unintended behavior in your program.