How to convert Set containing values into string

Question

public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str = "abcdaa";
        dups(str);
    }
    public static void dups(String str){
        HashSet hs = new HashSet();
        char[] ch = str.toCharArray();
        for(int i=0; i < ch.length;i++){
            hs.add(ch[i]);
        }
        System.out.println(hs);
    }

The above code return Output: [a,b,c,d]

But I want to print the Set values into a string so I can return a string value return value looks like this:Expected Output: abcd

Answer 1

 public static void main(String[] args) {
        // TODO Auto-generated method stub
        String str = "abcdaa";
        dups(str);
    }

    public static void dups(String str) {
        HashSet<Character> hs = new HashSet<Character>();
        char[] ch = str.toCharArray();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < ch.length; i++) {
            if(hs.add(ch[i])){
                sb.append(ch[i]);
            }
        }
        System.out.println(sb);
    }

EDIT

public static void dups(String str) {
            HashSet<Character> hs = new HashSet<Character>();
            StringBuilder sb = new StringBuilder();
            for (Character character : str.toCharArray()) {
                if(hs.add(character)){
                    sb.append(character);
                }
            }
            System.out.println(sb);
        }

I can't think a better way to do this... It's better use StringBuilder instead of String, check this answer https://stackoverflow.com/a/1532483/6949032

Answer 2

Not sure why no one had mentioned this yet, but it's pretty simple in Java 8:

System.out.println(String.join("", hs));

Note that if you want to preserve the original order, you'll need to use LinkedHashSet instead.