Removing an empty line with .replaceAll and regex in Java -

pardon if answered already. have hunted 2 days answer , got far. here problem solve:

write method called stripcomments accepts scanner representing input file containing java program parameter, reads file, , prints file's text comments removed. comment text on line // end of line, , text between /* , */ characters. example, consider following text:

import java.util.*;  /* program suzy student */ public class program {     public static void main(string[] args) {         system.out.println("hello, world!"); // println     }      public static /* hello there */ void foo() {         system.out.println("goodbye!"); // comment here     } /* */ } 

this came with:

public static void stripcomments(scanner scan) {     while(scan.hasnextline()) {         string str1 = scan.nextline();         string str2 = str1.replaceall("(/(\\*).*?(\\*)/)|(//.*?$)|(/(\\*).*?$)|([a-za-z\\s0-9]*?\\*(/))", "");         system.out.println(str2);     } } 

this result:

import java.util.*;       public class program {         public static void main(string[] args) {             system.out.println("hello, world!");          }          public static  void foo() {             system.out.println("goodbye!");          }      } 

while of correct, don't know how rid of line above "public class program {." how rid of line , there better way write regex expression?

thank in advance!

i came second replace command

str = str.replaceall("\n\\s*\n", "\n"); 

this requires pass in entire file though, wouldn't work line line.

if want continue going line line, should

if(str2.matches("\\s*"))     continue; 

p.s. last grouping of parenthesis around regex unnecessary if don't have quantifier. , multiline comment won't work 3+ lines, such as:

/*  *  * multiline  * comment  */ 

since passing in line line.