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I want to compare 2 array of different dimension and then eliminate the duplicate and put the result on array called tmp

Here is the code

ArrayList<String> list = new ArrayList<String>();
HashSet<String> tmp = new HashSet<String>();

try 
{
    String query1="SELECT ID FROM Apps;";
        ResultSet rs = con.createStatement().executeQuery(query1);
        while(rs.next())
        {
            list.add(rs.getString("ID"));
            tmp.add(rs.getString("ID"));
        }

        for(int i=0;i < check.size();i++)//ciclo  le checkbox selezionate
        {
                check.get(i);
                String query="UPDATE Apps SET Authorized='1' WHERE ID=" +check.get(i);//vado ad eseguire la query di update
                pr=con.prepareStatement(query);
                pr.executeUpdate();
                tmp.add(check.get(i).toString());
        }

        System.out.println(tmp);

The content of the two arrays is:

check -> [1, 2]
list -> [1, 2, 3, 4, 5]

The result I want is tmp -> [3,4,5]

but the console show tmp -> [1,2,3,4,5]

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5
  • try deleting the = in j<=check.size() Commented Jan 8, 2019 at 21:22
  • @Nosrep ok, i try but it doesn't work Commented Jan 9, 2019 at 8:02
  • Assuming check Always contains elements present in tmp, iterate over the elements in check and remove these from tmp. Commented Jan 9, 2019 at 9:04
  • @trappski please give me the code! Commented Jan 9, 2019 at 9:40
  • 1
    @lucapellegrini I suggest you check the answer posted by P.Raber and work from there. It's a clean an simple solution. Commented Jan 9, 2019 at 9:45

3 Answers 3

Reset to default
2

You could add everything to a hashSet

    HashSet<String> h = new HashSet<String>(); 

    // Adding elements into HashSet usind add() 
    h.add("Cats");
    h.add("Cats"):
    h.add("Dogs"); 

    System.out.println("List:" + h);

Output

List:[Dogs, Cats]

The hash set won't store any of the duplicates.

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1 Comment

I try, but it show me tmp -> [1,2,3,4,5] when i want tmp->[3,4,5]
1

You can remove duplicates like this:

    public static void main(String[] args) {

    Set<Integer> tmp = new HashSet<>();
    List<Integer> check = new ArrayList<>();
    check.add(1);
    check.add(2);
    List<Integer> list = new ArrayList<>();
    for(int i = 1; i <= 5; i++){
        list.add(i);
    }

    tmp.addAll(list);
    tmp.removeAll(check);
    System.out.println(tmp);
}
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1 Comment

Thanks!! This is the solution
-1

Try this

public static void main(String[] args)
  {
    List<String> one = new ArrayList<>();
    one.add("one");
    one.add("two");
    one.add("three");
    one.add("in one");
    one.add("in two");

    List<String> two = new ArrayList<>();
    two.add("zero");
    two.add("one");
    two.add("two");
    two.add("four");
    two.add("not in one");
    two.add("in one");
    two.add("in two");

    // Depending on your needs create new or modify existing like one.addAll(two) and stream() from that.
    List<String> unique = one;
    unique.addAll(two);
    unique = unique.stream().distinct().collect(Collectors.toList());

    System.out.println("Unique list: " + unique.stream().collect(Collectors.joining(",")));
    // Unique list: one,two,three,in one,in two,zero,four,not in one
  }
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1 Comment

I want to delete the duplicate in array unique.. the code doesn't work well

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