Removing duplicates in a Spinner in java when data comes from mySQL

Question

I am Using hashsetList to create a new list for my spinner without duplicates but java gives errors when I add this within the Spinner. Ithe project works fine when duplicates are shown from mySQL.

Here is the extract of MainActivity.java before I created the hashsetList.

  @Override
    protected void onPostExecute(Void args) {
        // Locate spinner1 in activity_main.xml
        Spinner spinner1 = (Spinner) findViewById(R.id.spinner1);

        // Spinner adapter

        spinner1.setAdapter(new ArrayAdapter<String>(MainActivity.this,
                android.R.layout.simple_spinner_dropdown_item,typesofjobs));

       Collections.sort(typesofjobs);

When I added the following hashsetList code to eliminate duplicates and run it, the project crashes.

  @Override
    protected void onPostExecute(Void args) {
        // Locate spinner1 in activity_main.xml
        Spinner spinner1 = (Spinner) findViewById(R.id.spinner1);


        Set<String> hashsetList = new HashSet<String>(typesofjobs);
        // Spinner adapter

        spinner1.setAdapter(new ArrayAdapter<String>(MainActivity.this,
                android.R.layout.simple_spinner_dropdown_item, (List<String>) hashsetList));

        Collections.sort(typesofjobs);

Am I putting hashsetList in the wrong place or using it incorrectly? I am just trying to replace "typesofjobs" with the non duplicate version. Is there a better way I could eliminate my spinner duplicates?

What is your error output and do you know the exact line where your program is crashing? — Tim Biegeleisen
– Tim Biegeleisen, Commented Oct 30, 2015 at 8:51

Community · Accepted Answer · 2017-05-23 10:27:11Z

1

You were on the right track when you used HashSet with your list to remove the duplicates. However, you made a mistake when you tried to cast this Set to a List, which won't work. Instead, in the code below I pass a LinkedHashSet created from your list of jobs into an ArrayList constructor. The resulting List will have all duplicate String job values removed.

@Override
protected void onPostExecute(Void args) {
    // Locate spinner1 in activity_main.xml
    Spinner spinner1 = (Spinner) findViewById(R.id.spinner1);

    List<String> typesofjobsunique = new ArrayList<>(new LinkedHashSet<>(typesofjobs));
    spinner1.setAdapter(new ArrayAdapter<String>(MainActivity.this,
            android.R.layout.simple_spinner_dropdown_item, typesofjobsunique));

    // not sure if you want to keep original list
    Collections.sort(typesofjobs);

Hat tip to this great SO post which discusses ways to remove duplicates from Java Lists.

edited May 23, 2017 at 10:27

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answered Oct 30, 2015 at 8:56

Tim Biegeleisen

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