How to find duplicate string from an Array of String [duplicate]

Answer 1

Add them all to a Set and you'll get unique users. Then convert it back to array.

Answer 2

Very simple, use LINQ to find duplicate in your list.

Answer 3

as you mentioned, there should not be duplicate entry, so better you iterate the whole array before adding new user, rather than adding and then checking for duplicates. the former solution would solve it in O(N).

Answer 4

If you need unique things then we have Set in java

  String[] users = "User1,User2,User1,User,User".split(",");

        Set<String> uniquUsers = new HashSet<String>();

        for (int i = 0; i < users.length; i++) {
            if (!uniquUsers.add(users[i]))
                users[i] = "Duplicate"; // here I am assigning Duplicate instead if find duplicate
                                        // you can assign as null or whatever you want to do with duplicates.
        }
        System.out.println(Arrays.toString(users));

Answer 5

If you want to make check on adding new user you just have to run through the array and use username.equals(*) on each existing user.

If you have an array with duplicate entries just run this algorythm for every user you have.

These are rough methods, there are a lot of optimizations for this problem.

Answer 6

create an array news_data and add strings in that.

for (int i = 0; i < news_data.length; i++) {
                for (int j = i+1; j < news_data.length; j++) {
                    if(news_data[i].equals(news_data[j])){
                        news_data = removeElement(news_data, j);
                    }
                }
            }
   public static String[] removeElement(String[] original, int element){
        String[] n = new String[original.length - 1];
        System.arraycopy(original, 0, n, 0, element );
        System.arraycopy(original, element+1, n, element, original.length - element-1);
        return n;
    }