Java: Removing comments from string

Question

I'd like to do a function which gets a string and in case it has inline comments it removes it. I know it sounds pretty simple but i wanna make sure im doing this right, for example:

private String filterString(String code) {
  // lets say code = "some code //comment inside"

  // return the string "some code" (without the comment)
}

I thought about 2 ways: feel free to advice otherwise

1. Iterating the string and finding double inline brackets and using substring method.
2. regex way.. (im not so sure bout it)

can u tell me what's the best way and show me how it should be done? (please don't advice too advanced solutions)

edited: can this be done somehow with Scanner object? (im using this object anyway)

Answer 1

If you want a more efficient regex to really match all types of comments, use this one :

replaceAll("(?:/\\*(?:[^*]|(?:\\*+[^*/]))*\\*+/)|(?://.*)","");

source : http://ostermiller.org/findcomment.html

EDIT:

Another solution, if you're not sure about using regex is to design a small automata like follows :

public static String removeComments(String code){
    final int outsideComment=0;
    final int insideLineComment=1;
    final int insideblockComment=2;
    final int insideblockComment_noNewLineYet=3; // we want to have at least one new line in the result if the block is not inline.
    
    int currentState=outsideComment;
    String endResult="";
    Scanner s= new Scanner(code);
    s.useDelimiter("");
    while(s.hasNext()){
        String c=s.next();
        switch(currentState){
            case outsideComment: 
                if(c.equals("/") && s.hasNext()){
                    String c2=s.next();
                    if(c2.equals("/"))
                        currentState=insideLineComment;
                    else if(c2.equals("*")){
                        currentState=insideblockComment_noNewLineYet;
                    }
                    else 
                        endResult+=c+c2;
                }
                else
                    endResult+=c;
                break;
            case insideLineComment:
                if(c.equals("\n")){
                    currentState=outsideComment;
                    endResult+="\n";
                }
            break;
            case insideblockComment_noNewLineYet:
                if(c.equals("\n")){
                    endResult+="\n";
                    currentState=insideblockComment;
                }
            case insideblockComment:
                while(c.equals("*") && s.hasNext()){
                    String c2=s.next();
                    if(c2.equals("/")){
                        currentState=outsideComment;
                        break;
                    }
                    
                }
                
        }
    }
    s.close();
    return endResult;   
}