Question

What are the differences between

int size = (int)((length * 200L) / 100L); // (1)

and

int size = length << 1; // (2)

(length is int in both cases)

I assume both code snippets want to double the length parameter.

I’d be tempted to use (2) … so are there any advantages for using (1)? I looked at the edge cases when overflow occurs, and both versions seem to have the same behavior.

Please tell me what am I missing.

Answer 1

And here is the 3rd option:

int size = length * 2; // Comment explaining what is 2 or what means this multiplication

And this must be the best option. As it is readable and easy to understand what you want to do.
As for performance, compilers are generating pretty optimized code, so no need to worry for such a simple operation.
If you have any concerns concerning overflow you can use checked block.

EDIT As mentioned by many others just use any meaningful variable instead of 2 here.