How to remove duplicates in following java code?

Question

I have written the following code and i am getting all the duplicates even i have used set.

private void validatingpswwithpattern(String password) throws IOException

  {
            List<String[]> list=new ArrayList<String[]>();
            list.add(new String[]{"raj","duvva","sathish"});
            list.add(new String[]{"raj","duvva","sathish"});
            list.add(new String[]{"raj","duvva","sathish"});
            list.add(new String[]{"raj","duvva","sathish"});
            list.add(new String[]{"raj","duvva","sathish"});
            list.add(new String[]{"raj","duvva","sathish"});


            Set<String[]> hs = new HashSet<String[]>();
             hs.addAll(list);
             list.clear();
             list.addAll(hs);
             System.out.println(list);
}

You are adding to the collection an arrays, which are compared by reference. That means all the objects are different, because all have a different references. — Stanislav, Oct 12 '15 at 13:23
visit following link. it might help you http://stackoverflow.com/a/21985571/4944490 — Krupesh Kotecha, Oct 12 '15 at 13:38

score 6 · Answer 1 · answered Oct 12 '15 at 13:23

Since arrays don't override the default implementation of hashCode and equals from Object class, HashSet is useless for eliminating duplicates.

You could use a TreeSet and supply a Comparator<String[]> that would determine when two String arrays are equal.

TreeSet<String[]> set = new TreeSet<> (new Comparator<String[]>() {
  public int compare(String[] o1, String[] o2)
  {
    // write here logic to determine whether o1<o2 (return -1) or
    //                                       o1>o2 (return 1) or 
    //                                       o1 is equal to o2 (return 0)
  }
});
set.addAll(list);

Shiladittya Chakraborty · Answer 2 · 2015-10-12T14:06:00.917

You can do in the following way. If you want to remove duplicate elements, then you can do something in this way.

List<String[]> list=new ArrayList<String[]>();
list.add(new String[]{"raj","duvva","sathish"});
list.add(new String[]{"raj","duvva","sathish"});
list.add(new String[]{"raj","duvva","sathish"});
list.add(new String[]{"raj","duvva","sathish"});
list.add(new String[]{"raj","duvva","sathish"});
list.add(new String[]{"raj","duvva","sathish"});

TreeSet<String[]> set = new TreeSet<String[]>(new Comparator<String[]>() {    
  @Override
  public int compare(String[] o1, String[] o2) {
    return Arrays.equals(o1, o2)? 0 : 1;
  }
});
set.addAll(list);

list = new ArrayList<String[]>(set);

score 0 · Answer 3 · answered Oct 12 '15 at 13:59

0

If you want to use HashSet you need to wrap your String[] into a List using Arrays.asList.

answered Oct 12 '15 at 13:59

LoganMzz

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How to remove duplicates in following java code?

3 Answers3