Android：比较数组列表中的字符串并将其组合

Question

I'm wanting to compare the strings in an array list taken from my database and join them together.. Here is the code which collects data from my database..

public List<String> getData2List() {
    String[] columns = new String[]{ KEY_ROWID, KEY_DATE, KEY_NAME, KEY_PRICE};
    Cursor c = ourDatabase.query(DATABASE_TABLE, columns, "1", null, null, null, null);

    List<String> results = new ArrayList<String>();
    int iCM = c.getColumnIndex(KEY_DATE);

    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
        results.add(c.getString(iCM));
    }
    return results;
}

and here is the code to place them in the list..

Database info = new Database(this);
    info.open();        

    List<String> dates = info.getData2List();
    lv.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, dates));

    info.close();

This all works fine but if there are more than one entry which is the same I end up with a list of the same thing (if this makes sense!?).

Example: if the list came out like {"01/01/13", "02/01/13", "01/01/13", "03/02/13", "01/01/13"} I'm trying to make the out come like {"01/01/13", "02/01/13", "03/02/13"} so that all entry of the same value have been compiled into one.

Any help or ideas is much appreciated.

Answer 1

Just use an Set instead of a List.

An HashSet will provide you unique strings, a List instead can contain same occurrence.

Answer 2

Why don't you just use HashSet<String> ?

Example:

List<String> dates = info.getData2List();
Set<String> uniqueDates = new HashSet<String>(dates);

Answer 3

You can use HashSet instead of ArrayList.

because in your case you will have following advantages

1. joining two set will be more easier useing addAll method
2. There is no chance to have duplicate values

Answer 4

You need a Set collection class, basically what "Set" does is, storing only unique values, and if you try to set a new value that already exist in the collection it will just ignore, make sure you are overriding equals, and hashCode method as well in case you are trying to store your own object, look at the documentation for more info about how it works..

http://docs.oracle.com/javase/6/docs/api/java/util/Set.html

Regards!