Counting the binary in a number java?

Question

I'm new to java and am wondering if there is any way to count the actual number of ones and zeros in the binary of a single int. For example, I would try and find out the number of 1's and zero's in the binary 32 bit binary of int 6?

Do it the same way you would in any other language you know and wrap the logic in a `main()` in a class. — noMAD, Sep 23 '14 at 20:59
See http://stackoverflow.com/a/5263199/3802841 to see how an int can be formatted as a string. Count either the '0's or the '1' and substract the count from the length of the string. — Markus Patt, Sep 23 '14 at 21:02

Jean Logeart · Answer 1 · 2014-09-23T21:20:00.063

7

Using Integer.bitcount(int):

int ones = Integer.bitCount(n);
int zeros = Integer.bitCount(~n) - Integer.numberOfLeadingZeros(n);

edited Sep 23 '14 at 21:20

answered Sep 23 '14 at 21:04

Jean Logeart

52,687
11
83
118

Good job giving away the answer. Great help for the OP – gkrls Sep 23 '14 at 21:06
Awesome. Who would have thought they'd already implemented this? http://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html#bitCount(int) – StriplingWarrior Sep 23 '14 at 21:06
@xgeorgekx Good job at answering the question? Thank you. – Jean Logeart Sep 23 '14 at 21:07
@xgeorgekx: You're going to downvote all the answers but yours? Really? – StriplingWarrior Sep 23 '14 at 21:08
I do not see any constructive answers. Anyone can just paste the code. – gkrls Sep 23 '14 at 21:10
I have implemented this and for an n value of 36 Integer.bitCount(~n) returns 30 somehow... Does it flip all of the bits that an integer could contain o.O? – Blake Yarbrough Sep 23 '14 at 21:13
Well, the question is: "Is there any way to count the actual number of ones and zeros in the binary of a single int". Yes there is using this method. What is there to explain? – Jean Logeart Sep 23 '14 at 21:14
@LanguidSquid Yes, I edited to avoid having ``zeros = 32 - ones`` – Jean Logeart Sep 23 '14 at 21:14
That's neat! Thanks, I didn't know about that utility on Integer – Blake Yarbrough Sep 23 '14 at 21:16

score 2 · Answer 2 · answered Sep 23 '14 at 21:07

2

Luckily, java has a built in method: Integer.toBinaryString() This takes an integer value, converts it to binary, then returns it as a String.

Or you could brush up on your java skills and create your own method to do it.

answered Sep 23 '14 at 21:07

DJ Fresh

38
4

score 1 · Answer 3 · answered Sep 23 '14 at 21:03

Since you provide no code i will give some guildines on how you can do it.

Get the binary represesantation of your int by calling this method Integer.toBinaryString(x);
The previous method will return only the nessecery bits of the number for example in the case of 6 it will return 110. But you need a 32 bit representation of 6 so you have to add the extra zeros in front of the result returned from that method.
create 2 counter variables. One for ones and one for zeros.
loop through the characters of your String and when a char == 0 increment the zeros counter. When char == 1 increment the ones counter.

Hope this helps

Why convert to ``String`` while the bits are *right there*, inside the ``int``? — Jean Logeart, Sep 23 '14 at 21:16

Counting the binary in a number java?

3 Answers3