variable |= variable meaning?

Question

I was looking trough some coding to extend my knowledge in Java and I came across the following line of code which I do not understand and googling returns nothing on the matter.

int metadata;
int facing;
metadata |= facing;

what does the |= mean/do is there documentation on this (Or more to the point what is this operation called)

Answer 1

"|" is boolean logical OR and placing the operand before "=" works pretty much the same as expressions like a += b (which means a = a + b).

So basically, a |= b is the same as a = a | b

List of all Java operands can be found here.

Answer 2

It is the same as

metadata = metadata | facing;

More on Java's operators here: http://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html

Answer 3

This is shorthand for

metadata = metadata | facing;