What is this expression in Java ( 1 << 2)?

Question

I don't know what this means "1 << 2" in :

public static final int MODIFY_METADATA = 1 << 2; // modify object

Please help me!

Similar questions have been asked and answered on SO, for example [here](http://stackoverflow.com/q/9207007/960195). — Adam Mihalcin, Mar 23 '12 at 01:47

score 6 · Answer 1 · answered Mar 23 '12 at 09:16

If you want to know why would use use 1 << 2 rather than 4 which is the same value, it because you explicitly want to be using a bit mask e.g.

public static final int FLAG0 = 1 << 0;
public static final int FLAG1 = 1 << 1;
public static final int MODIFY_METADATA = 1 << 2;

Shows each value is in a bit mask.

score 5 · Answer 2 · answered Mar 23 '12 at 01:41

5

<< is the left bit shift operator.

answered Mar 23 '12 at 01:41

Jeffrey

1

SO in your example, this is 1 bit shifted 2 to the left, which evalulates to 4 – Chris White Mar 23 '12 at 01:44
1

@ChrisWhite `1 << 2 = 4`, yes. – Jeffrey Mar 23 '12 at 01:45

2 Answers2