Java Switch

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Java Switch

2023-12-15 19:44| 来源: 网络整理| 查看: 265

Java Switch ❮ Previous Next ❯ Java Switch Statements

Instead of writing many if..else statements, you can use the switch statement.

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 value of the expression is compared with the values of each case. If there is a match, the associated block of code is executed. The break and default keywords are optional, and will be described later in this chapter

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)

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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"

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Note that if the default statement is used as the last statement in a switch block, it does not need a break.

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