The best performance implementation of counting the number of true of an integer?

Asked Sep 25 '20 at 16:06

Active Sep 25 '20 at 16:06

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I have an integer number, and the number can be expressed in 32 bits. And I want to count the number of true values.

For example: An integer 5566 can be expressed by 00000000 00000000 00010101 10111110, the number of true values is 9.

The calculation should consider the performance because it's used for a large data set.

In java, it seems that I need to convert the integer into byte[] first, and then convert into a boolean[] and then start counting, and I think there is a better way with better performance and less conversion.

asked Sep 25 '20 at 16:06

Steven Chou

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Are you talking about the number of one digits of the binary value? You can use 1 << n to check the nth bit. – NomadMaker Sep 25 '20 at 16:09
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Especially, see [this answer](https://stackoverflow.com/a/109054/10871900) mentioning `Integer.bitCount`. – dan1st Sep 25 '20 at 16:16
@NomadMaker yes. – Steven Chou Sep 25 '20 at 16:22
@dan1st Thank you! I'll check it. – Steven Chou Sep 25 '20 at 16:22

The best performance implementation of counting the number of true of an integer?

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