java program to remove duplicate words in a string

1public static void main(String[] args) {
2
3        String result = removeDup("AAABBBCCC");
4        System.out.println(result); // ABC
5
6public static  String  removeDup( String  str) {
7        String result = "";
8        for (int i = 0; i < str.length(); i++)
9            if (!result.contains("" + str.charAt(i)))
10                result += "" + str.charAt(i);
11        return result;
12    }
13}

1String fullString = "lol lol";
2String[] words = fullString.split("\\W+");
3StringBuilder stringBuilder = new StringBuilder();
4Set<String> wordsHashSet = new HashSet<>();
5
6for (String word : words) {
7    if (wordsHashSet.contains(word.toLowerCase())) continue;
8    wordsHashSet.add(word.toLowerCase());
9    stringBuilder.append(word).append(" ");
10}
11String nonDuplicateString = stringBuilder.toString().trim();

1String str1 = "ABCDABCD";
2String result1 = "";
3
4for (int a = 0; a <= str1.length()-1; a++) {
5if (result1.contains("" + str1.charAt(a))) { 
6// charAt methodda you provide index number ve sana character olarak donuyor,
7// If the string result does not contains str.CharAt(i), 
8// then we concate it to the result. if it does we will not
9   continue;
10}
11result1 += str1.charAt(a);
12}
13System.out.println(result1);