How to convert a binary representation of a string into byte in Java?

Question

as the title says, how do I do it? Its easy to convert from string -> byte -> string binary, But how do I convert back? Below is a example. The output is : 'f' to binary: 01100110 294984

I read somewhere that I could use the Integer.parseInt but clearly that is not the case :( Or am I doing something wrong?

Thanks, :)

public class main{
    public static void main(String[] args) {

         String s = "f";
          byte[] bytes = s.getBytes();
          StringBuilder binary = new StringBuilder();
          for (byte b : bytes)
          {
             int val = b;
             for (int i = 0; i < 8; i++)
             {
                binary.append((val & 128) == 0 ? 0 : 1);
                val <<= 1;
             }
             binary.append(' ');
          }
          System.out.println("'" + s + "' to binary: " + binary);

        System.out.println(Integer.parseInt("01100110", 2));
    }
}

You desperately need to clarify your requirement.

Hot Licks
– Hot Licks

2013-09-04 20:10:37 +00:00
Commented Sep 4, 2013 at 20:10 — Hot Licks
– Hot Licks, Commented Sep 4, 2013 at 20:10

arshajii · Accepted Answer · 2013-09-03 19:30:49Z

16

You can use Byte.parseByte() with a radix of 2:

byte b = Byte.parseByte(str, 2);

Using your example:

System.out.println(Byte.parseByte("01100110", 2));

answered Sep 3, 2013 at 19:30

arshajii

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4 Comments

Hot Licks Over a year ago

Except that the OP (if he is to be believed) wants to convert to binary text string.

Hot Licks Over a year ago

(Though on re-reading, it's impossible to tell what the OP wants.)

thomas.mc.work Over a year ago

That doesn't work for values greater than 01111111 == 127 as Byte has a range from -128 to 127.

arshajii Over a year ago

@thomas.mc.work Right but the OP just wants bytes; reread the question.

JNL · Accepted Answer · 2013-09-03 19:35:22Z

1

You can parse it to an integer in base 2, and convert to a byte array. In your example you've got 16 bits you can also use short.

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

byte[] array = bytes.array();

Just in case if you need it for a Very Big String.

String b = "0110100001101001";
byte[] bval = new BigInteger(b, 2).toByteArray();

answered Sep 3, 2013 at 19:35

JNL

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1 Comment

Hot Licks Over a year ago

Except that the OP (if he is to be believed) wants to convert to binary text string.

westberg · Accepted Answer · 2013-09-04 19:26:36Z

I made like this, converted a string s -> byte[] and then used Integer.toBinaryString to get binaryStringRep. I converted bianryStringRep by using Byte.parseByte to get the bianryStringRep into byte and the String(newByte[]) to get the byte[] into a String! Hope it helps others then me aswell! ^^

public class main{
    public static void main(String[] args) throws UnsupportedEncodingException {

         String s = "foo";
          byte[] bytes = s.getBytes();
          byte[] newBytes = new byte[s.getBytes().length];
          for(int i = 0; i < bytes.length; i++){
              String binaryStringRep = String.format("%8s", Integer.toBinaryString(bytes[i] & 0xFF)).replace(' ', '0');
              byte newByte = Byte.parseByte(binaryStringRep, 2);
              newBytes[i] = newByte;
          }

        String str = new String(newBytes, "UTF-8");
        System.out.println(str);
    }
}

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