Question

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Good tutorials on Bitwise operations in Java
Are the &, |, ^ bitwise operators or logical operators?

Code as below:

int rgb[] = new int[] {     
(argb >> 16) & 0xff, //red     
(argb >>  8) & 0xff, //green     
(argb      ) & 0xff  //blue 
}; 

I saw a code which is getting RGB value from a INT value, the operations are as above, but I never see such operation before, I want to find more information about what are they and what can they do, The symbol >> and & and 0xff.

So, what do you all address them in Java?

Answer 1

Further explanation of the bit arithmetic. Let’s assume the int bits look as follows:

00000000 10101010 01010101 11011011
unused   red      green    blue

To get the int value for blue, you want all bits other than the lower 8 turned off. The easy way to do this is with a bitwise and. 0xff can also be written as 0x000000ff, which will set the upper 24 bits to 0, and only turn on the bits in the lower 8 which are already set to 1.

argb & 0xff ==> 00000000 00000000 00000000 11011011
                                           blue

argb >> 8 ==> 00000000 00000000 10101010 01010101 
                                red      green
(argb >> 8) & 0xff ==> 00000000 00000000 00000000 01010101 
                                                  green

argb >> 16 ==> 00000000 00000000 00000000 10101010
                                          red
(argb >> 16) & 0xff ==> 00000000 00000000 00000000 10101010
                                                   red

even thought the & 0xff on the red value seems unecessary, there’s no guarantee the caller might not have set some of the high order unused bits, so you want to be safe and turn all of them off.