What's the different btw : comments, multi-lne comments and doc comments?

Answer 1

The idea of comment and multi-line comment is the same you are hiding from compiler part of code.
You can put multi-line comment(/*...*/) for the block of code or comment(//) all lines of that block. It's the same.

Answer 2

Yeah, they both make lines you can read, but the computer ignores, however multiline comments
/*
allow your comments to take up multiple lines.
*/
and single line comments
//will end before the next line.
Javadoc comments function the same as multiline comments, they just look better and cleaner.

Answer 3

ah. so in the end it's the same idea we're talking abt here. 😃thnx I appreciate it ^^