如何使用regex与String.split()

I have the following String:

我有以下字符串:

String fullPDFContex = "Title1 Title2\r\nTitle3 Title4\r\n\r\nTitle5 Title6\r\n \r\n Title7 \r\n\r\n\r\n\r\n\r\n"
Strin