removing invalid characters ((“\\/:*?\”|”) ) from a string to use it as a FileName

You can try this,

String fileName = "\\/:*AAAAA?\"<>|3*7.pdf";
String invalidCharRemoved = fileName.replaceAll("[\\\\/:*?\"<>|]", "");
System.out.println(invalidCharRemoved);

OUTPUT

AAAAA37.pdf