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up vote 2 down vote favorite

I have a string of ones and zeros that I want to convert to an array of bytes.

For example String b = "0110100001101001" How can I convert this to a byte[] of length 2?

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Why of length 2 ? –  kocko Jul 18 '13 at 15:11
1  
@kocko he has 16 bits... –  Heuster Jul 18 '13 at 15:13
    
Based off of string b, you want a byte[] length 2 with 104 in position 0, and 105 in position 1? –  Saviour Self Jul 18 '13 at 15:18
    
possible duplicate of convert a string to byte array –  Shashi Jul 25 '13 at 7:37
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2 Answers

up vote 12 down vote accepted

Parse it to an integer in base 2, then convert to a byte array. In fact, since you've got 16 bits it's time to break out the rarely used short.

short a = Short.parseShort(b, 2);
ByteBuffer bytes = ByteBuffer.allocate(2).putShort(a);

byte[] array = bytes.array();
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What if the String contains too many bits that it can't be hold even in a long variable? –  Luiggi Mendoza Jul 18 '13 at 15:14
    
This is very cool! I didn't know it, thanks! :) –  kocko Jul 18 '13 at 15:14
    
If the string is too big, then you'll get a NumberFormatException. I'm making assumptions that it's less than 32 characters for this small example. –  Jeff Foster Jul 18 '13 at 15:17
    
Then this is not a bullet-proof solution. Is there any with simple code or it involves manual working on the String contents? –  Luiggi Mendoza Jul 18 '13 at 15:19
2  
I'm not sure this could get much simple? If b is in an invalid format a NumberFormatException will be thrown and it's up to the callee to handle the error. Open to suggestions on how to improve this, but I think this is enough of an answer to illustrate the point. –  Jeff Foster Jul 18 '13 at 15:23
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up vote 5 down vote

Another simple approach is:

String b = "0110100001101001";
byte[] bval = new BigInteger(b, 2).toByteArray();
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it cannot parse "1110100001101001" –  Evgeniy Dorofeev Aug 29 '13 at 7:03
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