java bitwise operators and the equal character; compound operators

Question

I'm a bit confused:

long v = 0;
v <<= 8; 
v |= 230;

I know << is the signed left shift operator and | Bitwise the inclusive OR but I'm confused to what the equals does?

So fist v is 0. So << doesn't have any effect? Then it equals 1000 but what happens then?

edit: I've edited the title so others might better find this question: added "compound operators"

Answer 1

They're compound operators, like += and -= are. They do the operation, and then assign the result back to v .

Basically:

v <<= 8;

is in effect

v = v << 8;

And similarly

v |= 230;

is in effect

v = v | 230;

You can see the parallel with += and -= :

v += 1;

is effectively

v = v + 1;

Answer 2

There are somewhat like += .

For example x+=3 means add 3 to x; store to x.

v <<= 8;

left-shifts v 8 bits, and stores to v, functionally equivalent to v=v << 8 .

v |= 230;

does a bitwise OR with 230 and stores back to v, equivalent to v=v | 230 v=v | 230 .

Now, due to performance constraints and optimizations this operation may be done in place at a low level.

Answer 3

Basically, this:

v <<= 8; 
v |= 230;

is equivalent to this:

v = v << 8; 
v = v | 230;