How do I remove repeated elements from ArrayList?

Question

I have an ArrayList<String>, and I want to remove repeated strings from it. How can I do this?

Answer 1

LinkedHashSet will do the trick.

String[] arr2 = {"5","1","2","3","3","4","1","2"};
Set<String> set = new LinkedHashSet<String>(Arrays.asList(arr2));
for(String s1 : set)
    System.out.println(s1);

System.out.println( "------------------------" );
String[] arr3 = set.toArray(new String[0]);
for(int i = 0; i < arr3.length; i++)
     System.out.println(arr3[i].toString());

//output: 5,1,2,3,4

Answer 2

for(int a=0;a<myArray.size();a++){
        for(int b=a+1;b<myArray.size();b++){
            if(myArray.get(a).equalsIgnoreCase(myArray.get(b))){
                myArray.remove(b); 
                dups++;
                b--;
            }
        }
}

Answer 3

In Java 8:

List<String> deduped = list.stream().distinct().collect(Collectors.toList());

Please note that the hashCode-equals contract for list members should be respected for the filtering to work properly.

Answer 4

It is possible to remove duplicates from arraylist without using HashSet or one more arraylist.

Try this code..

    ArrayList<String> lst = new ArrayList<String>();
    lst.add("ABC");
    lst.add("ABC");
    lst.add("ABCD");
    lst.add("ABCD");
    lst.add("ABCE");

    System.out.println("Duplicates List "+lst);

    Object[] st = lst.toArray();
      for (Object s : st) {
        if (lst.indexOf(s) != lst.lastIndexOf(s)) {
            lst.remove(lst.lastIndexOf(s));
         }
      }

    System.out.println("Distinct List "+lst);

Output is

Duplicates List [ABC, ABC, ABCD, ABCD, ABCE]
Distinct List [ABC, ABCD, ABCE]

Answer 5

This three lines of code can remove the duplicated element from ArrayList or any collection.

List<Entity> entities = repository.findByUserId(userId);

Set<Entity> s = new LinkedHashSet<Entity>(entities);
entities.clear();
entities.addAll(s);

Answer 6

ArrayList<String> city=new ArrayList<String>();
city.add("rajkot");
city.add("gondal");
city.add("rajkot");
city.add("gova");
city.add("baroda");
city.add("morbi");
city.add("gova");

HashSet<String> hashSet = new HashSet<String>();
hashSet.addAll(city);
city.clear();
city.addAll(hashSet);
Toast.makeText(getActivity(),"" + city.toString(),Toast.LENGTH_SHORT).show();