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!

+3

thuclh 23 Mar 12 at 1:39

2 answers

Jeffrey · Answer 1 · 2012-03-23T01:41:18+0000

<<

- left bit shift operator.

Peter lawrey · Answer 2 · 2012-03-23T09:16:03+0000

If you want to know why use use 1 << 2

and not 4, which is the same value, it is because you explicitly want to use a bitmask, eg.

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

Indicates that each value is in a bit mask.