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if else or switch

Posted on 2011-03-18
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Last Modified: 2012-05-11
Hi

This is a very common question that is similar to every programming.

My query is which language construct to use when and which is quicker.
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Question by:KaranGupta
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Pratima Pharande earned 167 total points
ID: 35164443
switch statement is faster to execute than the if-else-if ladder. This is due to the compiler's ability to optimise the switch statement. In the case of the if-else-if ladder, the code must process each if statement in the order determined by the programmer. However, because each case within a switch statement does not rely on earlier cases, the compiler is able to re-order the testing in such a way as to provide the fastest execution.
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by:Pratima Pharande
ID: 35164448
when tou have one or two conditions go for if elese.
if you have ladderof if else if then go for switch
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Assisted Solution

by:mayank_joshi
mayank_joshi earned 167 total points
ID: 35164461
As with most things you should pick which to use based on the context and what is conceptually the correct way to go. A switch is really saying "pick one of these based on this variables value" but an if statement is just a series of boolean checks.

As an example, if you were doing:

int value = // some value
if (value == 1) {
    doThis();
} else if (value == 2) {
    doThat();
} else {
    doTheOther();
}

This would be much better represented as a switch as it then makes it immediately obviously that the choice of action is occurring based on the value of "value" and not some arbitrary test.

Also, if you find yourself writing switches and if-elses and using an OO language you should be considering getting rid of them and using polymorphism to achieve the same result if possible.

Finally, regarding switch taking longer to type, I can't remember who said it but I did once read someone ask "is your typing speed really the thing that affects how quickly you code?" (paraphrased)
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Assisted Solution

by:openshac
openshac earned 166 total points
ID: 35164472
There are some performance tests at:

http://www.blackwasp.co.uk/SpeedTestIfElseSwitch.aspx

"The results show that the switch statement is faster to execute than the if-else-if ladder. This is due to the compiler's ability to optimise the switch statement. In the case of the if-else-if ladder, the code must process each if statement in the order determined by the programmer. However, because each case within a switch statement does not rely on earlier cases, the compiler is able to re-order the testing in such a way as to provide the fastest execution."
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LVL 11

Expert Comment

by:SAMIR BHOGAYTA
ID: 35167891
Hello, If you want the application is quickly execute then my advice is you should use the switch() case .
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Author Closing Comment

by:KaranGupta
ID: 35180028
Thanks
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