Flash cards
Review the key moves
What is the main idea behind Java Switch?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
___( expression ) {Put the learning moves in the order that makes the concept easiest to apply.
Java Switch Statements
Instead of writing many if..else statements, you can use the switch statement.
Think of it like ordering food in a restaurant: If you choose number 1, you get Pizza. If you choose 2, you get a Burger. If you choose 3, you get Pasta. Otherwise, you get nothing .
The switch statement selects one of many code blocks to be executed:
Syntax
switch( expression ) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}This is how it works
- The switch expression is evaluated once.
- The result is compared with each case value.
- If there is a match, the matching block of code runs.
- The break statement stops the switch after the matching case has run.
- The default statement runs if there is no match.
The example below uses the weekday number to calculate the weekday name:
Example
int day = 4;
switch (day) {
case 1: System.out.println("Monday");
break;
case 2: System.out.println("Tuesday");
break;
case 3: System.out.println("Wednesday");
break;
case 4: System.out.println("Thursday");
break;
case 5: System.out.println("Friday");
break;
case 6: System.out.println("Saturday");
break;
case 7: System.out.println("Sunday");
break;
}
// Outputs "Thursday" (day 4)The break Keyword
When Java reaches a break keyword, it breaks out of the switch block.
This will stop the execution of more code and case testing inside the block.
When a match is found, and the job is done, it's time for a break. There is no need for more testing.
A break can save a lot of execution time because it "ignores" the execution of all the rest of the code in the switch block.
The default Keyword
The default keyword specifies some code to run if there is no case match:
Example
int day = 4;
switch (day) {
case 6: System.out.println("Today is Saturday");
break;
case 7: System.out.println("Today is Sunday");
break;
default: System.out.println("Looking forward to the Weekend");
}
// Outputs "Looking forward to the Weekend"Note that if the default statement is used as the last statement in a switch block, it does not need a break.