If you need to find text lines that start with an alphanumeric characters:

String reg ="\\w+";  

In other words, an alphanumeric character that gets repeated 1 or more times.

 To find text lines that start with a whitespace and contain other characters after it, use the following regex:

String  reg = "\\s.+";

 That is, first find a whitespace, then any character repeated 1 or more times.