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 m

Answer 1

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.