JAVA - Write binary number to a file and read it

Question

How can i write to a file a binary number without it to cut the zeros .

I'm writing like this :

byte[] b = new BigInteger("1011010101010110", 2).toByteArray();

FileOutputStream fos = new FileOutputStream("file",true);
fos.write(b);

But then for example : When i write 0000001, it writes in the file just 1 and ignores the zeros, the same happens if i write 001001001000 , it ignores the zeros on the left reading 8bits at the time from the right to the left.

What is the correct way to write binary digits to a file ? If this is the correct way, i'm might be trying to read the file in the wrong way ( I'm using the read() of InputStream )

Ps-(8 digits must be 1 byte so writing as a string is not an option, cause each digit is 1 byte.)

Write is as a String. Try stackoverflow.com/questions/1053467/… and then parse it into binary — jesantana
– jesantana, Commented Apr 1, 2013 at 13:01

Evgeniy Dorofeev · Accepted Answer · 2013-04-01 13:03:07Z

1

You can try something like this

    String s = "0000001";
    byte[] a = new byte[s.length()];
    for (int i = 0; i < s.length(); i++) {
        a[i] = (byte) (s.charAt(i) & 1);
    }

answered Apr 1, 2013 at 13:03

Evgeniy Dorofeev

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4 Comments

CmchPt Over a year ago

But like that, it takes me 7 bytes to write it one the file.. "0000001" must take only 1 byte.

Evgeniy Dorofeev Over a year ago

But you said 'When i write 0000001, it writes in the file just 1 and ignores the zeros'

CmchPt Over a year ago

Yes I know, but there is no way to saving the 0000001 in 1 byte ? without loosing the zeros ?

Evgeniy Dorofeev Over a year ago

When you save a byte you always save all 8 bits with leading 0s if any. You need a hex viewer to see all bits.

CodeChimp · Accepted Answer · 2013-04-01 12:59:15Z

0

You don't want to write it as a binary, you want to write it as a String representing the binary. The problem is that Java has no way to know you want it padded. I would suggest converting your binary numbers to a String, then left-padding with 0 (Apache StringUtils will help with this)

answered Apr 1, 2013 at 12:59

CodeChimp

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