How does "" (double quote symbol) have methods?

Question

How can a double quote ("") have a method even if you didn't actually declared it in a String. Like for example:

System.out.println("".length());

is "" an object already without declaring it on a String? or is it a keyword on Java that he knows it is already a string in the making?

Answer 1

JLS §3.10.5 explains what string literals are ("A string literal consists of zero or more characters enclosed in double quotes.") and also says:

A string literal is always of type String (§4.3.3).