public class   ExtractIt
{
    private String url;

    public static void main(String[] args) {
    String s =  ExtractIt.extractIt("http://example.com/files/public_files/test.zip");
    String m =  ExtractIt.extractIt("www.abc.com/pub/*aaa.html");
    System.out.println(s);
    System.out.println(m);
    }

    public static String extractIt (String url)
    {
        String[] s1  = url.split("/");
        int i = s1.length; // s1เอามาหาindex
        String s2 = s1[i-1];

        if(s2.startsWith(""))

         return "_" + s2.substring(1);

        else
         return s2;

    }

}