Syntax in Java math operations (bitwise or equals)

Question

Google doesn\'t seem to help with the following: in Java, what does the following mean?

long_num1 |= long_num2

Answer 1

Means long_num1 = long_num1 | long_num2.

The | is bitwise OR.

Answer 2

It's a bitwise OR logical operation.

1 | 0 = 1
1001 | 0101 = 1101
11110000 | 00001111 = 11111111

It's commonly used when one has to deal with bit fields. The long_num values store multiple Boolean flags as individual bits of the whole integer.

Note however that Java has a built-in feature for dealing with bit fields: the BitSet class.