How to convert byte to binary in java?

Question

I have attempted convert from 10000101 to -123 by code

byte sum = (byte) (Integer.valueOf(10000101, 2) & 0xffff) ";

now I don't know how to convert back from -123 to 10000101.

Any suggestions about using java API to do conversion?

Are you aware of the `toBinaryString` method of the `Integer` class? — Dawood ibn Kareem, Nov 19 '16 at 09:13
@community.. it is not the same question.. OP here asks to convert a byte to a binary string.. it's a completely different question... — user6904265, Nov 19 '16 at 10:56

user6904265 · Accepted Answer · 2016-11-19T09:43:43.750

Expanding a bit the David Wallace comment, you can do it with this code:

    String fromByteToString = String.format("%8s", Integer.toBinaryString(sum & 0xFF)).replace(' ', '0');
    System.out.println(fromByteToString);

with sum & 0xFF you do the bitwise AND operation:

-123 = 11111111111111111111111110000101
0xFF = 00000000000000000000000011111111
res. = 00000000000000000000000010000101

Note that the replace(' ', '0') is not a must in this case because the binary result string starts (10000101) with 1.

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