java, regular expression, need to escape backslash in regex

Question

With reference to below question - String.replaceAll single backslashes with double backslashes

I wrote a test program, and I found that the result is true in both

Answer 1

The first form \\t will be expanded to a tab char by the pattern class.

The second form \t will be expanded to a tab char by Java before it builds a pattern.

In the end, you get a tab char either way.