CODEWITHSUNDEEP
javabitwise-operators
user3107774
user3107774

Reputation: 101

Why is this bitwise operation not working?

Ok this is probably something really stupid, but I can't understand why this isn't working;

    byte temp = (byte)0x80;
    System.out.println(temp);
    byte holder = (byte)(temp | 0x40);
    System.out.println(holder);

Produces:

-128

-64

Shouldn't a bitwise or on:

10000000

01000000

Yield

11000000

or -192?

Upvotes: 3

Views: 86

Answers (2)

Jean-François Savard
Jean-François Savard

Reputation: 21004

0x80 represent 128 and 0x40 represent 64. If you print 0x80 | 64 it will output 192.

When you cast to byte 128 becomes -128 as 128 is higher then Byte.MAX_VALUE which is 127.

So the expression you evaluate is -128 | 64, while you were probably expecting 128 | 64, and will result in your output, -64.

Upvotes: 3

biddyfiddy
biddyfiddy

Reputation: 51

Try printing them out this way instead:

byte b1 = (byte)0x80; String s1 = String.format("%8s", Integer.toBinaryString(b1 & 0xFF)).replace(' ', '0'); System.out.println(s1); byte b2 = (byte)0x40; String s2 = String.format("%8s", Integer.toBinaryString(b2 & 0xFF)).replace(' ', '0'); System.out.println(s2); byte b3 = (byte)(b1 | b2); String s3 = String.format("%8s", Integer.toBinaryString(b3 & 0xFF)).replace(' ', '0'); System.out.println(s3);

Upvotes: 0

Related Questions